I wanted to put together a list of pistol calibers, so here goes. If anything was left out please feel free to add to the list. Some of the information in this article was pulled from wikipedia - http://en.wikipedia.org
22 Long Rifle: .22 Long is a variety of .22 caliber (5.56 mm) rimfire ammunition. The .22 Long is the second oldest of the surviving rimfire cartridges, dating back to 1871, when it was loaded with a 29 grain (1.9 g) bullet and 5 grains (0.32 g) of black powder, 25% more than the .22 Short it was based on. It was designed for use in revolvers, but was soon chambered in rifles as well. The .22 Long Rifle, a heavier loading of the .22 Long case, appeared in 1887, along with the first smokeless powder loadings of the .22 rimfires. The 22 long rifle is perfectly suited for small game, such as rabbits, squirrels and raccoons. During the great depression, the 22 gained great popularity due to the fact that is was inexpensive. Rural families could use this inexpensive round to hunt small game with.
25 ACP: The .25 ACP (6.35 mm) centerfire pistol cartridge is a semi-rimmed, straight-walled pistol cartridge designed by John Browning in 1906. In modern times, the 25 auto is more of a novelty. Most people will buy either a pistol chambered in 22 long rifle or a 380 instead of a 25.
380 Auto: The .380 ACP (Automatic Colt Pistol) (also referred to as the "9mm Short", "9mm Browning", "9 mm Kurz", "9mm Corto", "9x17mm") pistol cartridge is a rimless, straight-walled pistol cartridge developed by firearms designer John Browning. It was introduced in 1908 by Colt, and has been a popular self-defense cartridge ever since. Many police officers opt for a 380 as their back-up pistol. The 380 is also favored for its lite recoil as compared to other pistols.
9 mm Makarov: The 9x18mm caliber was the standard pistol caliber for Eastern European countries, many of which still use this caliber today. 9x18mm caliber uses a larger diameter bullet than other 9mm rounds. 9mm Parabellum is 9.017mm (0.355 inches), however 9x18mm rounds are loaded with bullets measuring 9.220mm (0.363 inches). As a result, different bullets must be used to load 9x18mm cartridges. The 9x18 bullet is actually slightly larger in diameter than standard 9mm Parabellum.
9mm Luger: The 9mm Parabellum pistol cartridge was introduced in 1902 by the German weapons manufacturer Deutsche Waffen und Munitionsfabriken (DWM) for their Luger pistol. It was a higher-power version of the earlier 7.65mm Luger Parabellum, itself developed from an earlier 7.65mm Borchardt cartridge. During the 1980's the US military started looking at 9mm pistols to replace the 45 acp. The M9 9mm pistol was adopted by the military in the 1980's. It is essentially a mil-spec Beretta 92F, later the 92FS.
38 special: .38 Special is a rimmed, centerfire cartridge designed by Smith & Wesson. It is most commonly used in revolvers, although semi-automatic pistols and some carbines also use this round. The .38 Special was the standard service cartridge of most police departments in the United States from the 1920s to the 1980s. Even though the 38 special has been replaced as a service round, it is still used for target shooting. The round is easy and cost effective to reload.
38 Super Auto The 38 Super was introduced in the late 1920s as a higher pressure loading of the .38 ACP. The old .38 ACP propelled a 130 grain bullet at 1050 feet per second (fps). The improved .38 Super Auto pushed the same 130 grain bullet at 1280 fps. The .38 Super has gained distinction as the caliber of choice for many top pistol match competitors. In overall sales, it lags far behind most other pistol cartridges today.
357 magnum: The .357 Magnum was developed over a period of time in the early to mid-1930s in a direct response to Colt's .38 Super Automatic. This cartridge is regarded by many as an excellent self-defense round; it still enjoys a reputation of being the gold standard of stopping power among handgun cartridges. Guns in .357 Magnum caliber have the advantage of being able to fire .38 Special ammunition, with its lower cost, recoil, noise, muzzle flash, and, often, better accuracy.
357 Sig: SIGARMS, in partnership with Federal Cartridge, developed the 357 SIG cartridge in 1994. Contrary to popular belief, the 357 SIG cartridge is not a .40 S&W case necked down to accept .355 inch bullets. The goal of the 357 SIG project was to offer at least the level of performance of lighter .357 Magnum loads and +P/+P+ 9 mm Luger loads. The 357 SIG accomplishes this goal with a 125-grain (8.1 g) bullet.
40 S&W: The .40 S&W is a rimless cartridge developed jointly by Winchester and Smith & Wesson. The round debuted January 17, 1990. The 40 S&W can fire a 155 gr JHP @ 1140 fps with 432 ft·lbf.
10 mm Auto: The 10 mm Auto is a powerful and versatile cartridge for semi-automatic pistols, developed by ammunition manufacturer FFV Norma AB of Åmotfors, Sweden, and introduced in 1983 in the ill-fated Bren Ten pistol.
41 Magnum: In 1963, Elmer Keith and Bill Jordan petitioned Smith & Wesson, Remington, and Norma to produce a revolver and cartridge in this caliber to overcome perceived shortcomings in the extant .357 Magnum and .44 Magnum caliber cartridges. The .41 Magnum has never had the success of either the .357 or .44 Magnum cartridges, but was still prized by some handgunners as a hunting cartridge. For the largest game, though, a .44 Magnum with its ability to use a heavier bullet is still preferred.
44 Magnum: The .44 Magnum cartridge was the result of "souped-up" handloading of the .44 Special. The .44 Special, and other big bore handgun cartridges were being loaded with heavy bullets pushed at higher than normal velocities for better hunting performance. The .44 Magnum case is slightly longer than the .44 Special case, not because of the need for more room for propellant, but to prevent the more powerful cartridge from being chambered in older, weaker .44 Special firearms.
45 ACP: The .45 ACP (Automatic Colt Pistol, 11.43 x 23 mm) is a rimless pistol cartridge designed by firearms designer John Browning in 1905, for use in his prototype Colt semi-automatic .45 pistol—a design which evolved into the M1911 pistol adopted by the U.S. Army in 1911. The .45 ACP would become one of the most successful cartridges of all time, among both military and civilian users. It has been used in innumerable handguns and submachine guns (including most famously in the M1911 pistol) since its introduction.
45 Long Colt: The .45 Colt cartridge (known commonly as the ".45 Long Colt ") was developed by the US Army at Frankfort Arsenal in 1872 as an improvement of the British .476 Eley to replace the standard issue Smith and Wesson .44 round in the famous Colt Single Action Army, often known as the Peacemaker single action revolver.
454 Casull: The .454 Casull was, developed in 1957 by **** Casull and Jack Fulmer. It was first announced in November 1959 by Guns and Ammo magazine. The basic design was a lengthened and structurally improved .45 Colt case.
50 AE: The .50 Action Express (AE, 12.7 x 32.6 mm) is a large caliber handgun cartridge. It was developed in 1988 by Evan Whildin of Action Arms. The Magnum Research Desert Eagle was the first handgun chambered for the .50 AE. Among the few commercial handgun cartridges designed that exceed its ballistic performance are the .454 Casull, .460 S&W Magnum and the .500 S&W Magnum.
500 S&W Magnum: The .500 S&W Magnum is a cartridge that was developed by CorBon for Smith & Wesson for use in their Model 500 revolvers and introduced in February 2003 at the SHOT trade show. It is the most powerful handgun cartridge commercially manufactured with over 2500 ft·lbf (3.5 kJ) of energy created with a 440gr bullet travelling at 1625 fps. Some loadings can even achieve muzzle velocities of 2300 fps using a 325 grain bullet. This produces a muzzle energy of over 3817 ft·lbf.
22 Long Rifle: .22 Long is a variety of .22 caliber (5.56 mm) rimfire ammunition. The .22 Long is the second oldest of the surviving rimfire cartridges, dating back to 1871, when it was loaded with a 29 grain (1.9 g) bullet and 5 grains (0.32 g) of black powder, 25% more than the .22 Short it was based on. It was designed for use in revolvers, but was soon chambered in rifles as well. The .22 Long Rifle, a heavier loading of the .22 Long case, appeared in 1887, along with the first smokeless powder loadings of the .22 rimfires. The 22 long rifle is perfectly suited for small game, such as rabbits, squirrels and raccoons. During the great depression, the 22 gained great popularity due to the fact that is was inexpensive. Rural families could use this inexpensive round to hunt small game with.
25 ACP: The .25 ACP (6.35 mm) centerfire pistol cartridge is a semi-rimmed, straight-walled pistol cartridge designed by John Browning in 1906. In modern times, the 25 auto is more of a novelty. Most people will buy either a pistol chambered in 22 long rifle or a 380 instead of a 25.
380 Auto: The .380 ACP (Automatic Colt Pistol) (also referred to as the "9mm Short", "9mm Browning", "9 mm Kurz", "9mm Corto", "9x17mm") pistol cartridge is a rimless, straight-walled pistol cartridge developed by firearms designer John Browning. It was introduced in 1908 by Colt, and has been a popular self-defense cartridge ever since. Many police officers opt for a 380 as their back-up pistol. The 380 is also favored for its lite recoil as compared to other pistols.
9 mm Makarov: The 9x18mm caliber was the standard pistol caliber for Eastern European countries, many of which still use this caliber today. 9x18mm caliber uses a larger diameter bullet than other 9mm rounds. 9mm Parabellum is 9.017mm (0.355 inches), however 9x18mm rounds are loaded with bullets measuring 9.220mm (0.363 inches). As a result, different bullets must be used to load 9x18mm cartridges. The 9x18 bullet is actually slightly larger in diameter than standard 9mm Parabellum.
9mm Luger: The 9mm Parabellum pistol cartridge was introduced in 1902 by the German weapons manufacturer Deutsche Waffen und Munitionsfabriken (DWM) for their Luger pistol. It was a higher-power version of the earlier 7.65mm Luger Parabellum, itself developed from an earlier 7.65mm Borchardt cartridge. During the 1980's the US military started looking at 9mm pistols to replace the 45 acp. The M9 9mm pistol was adopted by the military in the 1980's. It is essentially a mil-spec Beretta 92F, later the 92FS.
38 special: .38 Special is a rimmed, centerfire cartridge designed by Smith & Wesson. It is most commonly used in revolvers, although semi-automatic pistols and some carbines also use this round. The .38 Special was the standard service cartridge of most police departments in the United States from the 1920s to the 1980s. Even though the 38 special has been replaced as a service round, it is still used for target shooting. The round is easy and cost effective to reload.
38 Super Auto The 38 Super was introduced in the late 1920s as a higher pressure loading of the .38 ACP. The old .38 ACP propelled a 130 grain bullet at 1050 feet per second (fps). The improved .38 Super Auto pushed the same 130 grain bullet at 1280 fps. The .38 Super has gained distinction as the caliber of choice for many top pistol match competitors. In overall sales, it lags far behind most other pistol cartridges today.
357 magnum: The .357 Magnum was developed over a period of time in the early to mid-1930s in a direct response to Colt's .38 Super Automatic. This cartridge is regarded by many as an excellent self-defense round; it still enjoys a reputation of being the gold standard of stopping power among handgun cartridges. Guns in .357 Magnum caliber have the advantage of being able to fire .38 Special ammunition, with its lower cost, recoil, noise, muzzle flash, and, often, better accuracy.
357 Sig: SIGARMS, in partnership with Federal Cartridge, developed the 357 SIG cartridge in 1994. Contrary to popular belief, the 357 SIG cartridge is not a .40 S&W case necked down to accept .355 inch bullets. The goal of the 357 SIG project was to offer at least the level of performance of lighter .357 Magnum loads and +P/+P+ 9 mm Luger loads. The 357 SIG accomplishes this goal with a 125-grain (8.1 g) bullet.
40 S&W: The .40 S&W is a rimless cartridge developed jointly by Winchester and Smith & Wesson. The round debuted January 17, 1990. The 40 S&W can fire a 155 gr JHP @ 1140 fps with 432 ft·lbf.
10 mm Auto: The 10 mm Auto is a powerful and versatile cartridge for semi-automatic pistols, developed by ammunition manufacturer FFV Norma AB of Åmotfors, Sweden, and introduced in 1983 in the ill-fated Bren Ten pistol.
41 Magnum: In 1963, Elmer Keith and Bill Jordan petitioned Smith & Wesson, Remington, and Norma to produce a revolver and cartridge in this caliber to overcome perceived shortcomings in the extant .357 Magnum and .44 Magnum caliber cartridges. The .41 Magnum has never had the success of either the .357 or .44 Magnum cartridges, but was still prized by some handgunners as a hunting cartridge. For the largest game, though, a .44 Magnum with its ability to use a heavier bullet is still preferred.
44 Magnum: The .44 Magnum cartridge was the result of "souped-up" handloading of the .44 Special. The .44 Special, and other big bore handgun cartridges were being loaded with heavy bullets pushed at higher than normal velocities for better hunting performance. The .44 Magnum case is slightly longer than the .44 Special case, not because of the need for more room for propellant, but to prevent the more powerful cartridge from being chambered in older, weaker .44 Special firearms.
45 ACP: The .45 ACP (Automatic Colt Pistol, 11.43 x 23 mm) is a rimless pistol cartridge designed by firearms designer John Browning in 1905, for use in his prototype Colt semi-automatic .45 pistol—a design which evolved into the M1911 pistol adopted by the U.S. Army in 1911. The .45 ACP would become one of the most successful cartridges of all time, among both military and civilian users. It has been used in innumerable handguns and submachine guns (including most famously in the M1911 pistol) since its introduction.
45 Long Colt: The .45 Colt cartridge (known commonly as the ".45 Long Colt ") was developed by the US Army at Frankfort Arsenal in 1872 as an improvement of the British .476 Eley to replace the standard issue Smith and Wesson .44 round in the famous Colt Single Action Army, often known as the Peacemaker single action revolver.
454 Casull: The .454 Casull was, developed in 1957 by **** Casull and Jack Fulmer. It was first announced in November 1959 by Guns and Ammo magazine. The basic design was a lengthened and structurally improved .45 Colt case.
50 AE: The .50 Action Express (AE, 12.7 x 32.6 mm) is a large caliber handgun cartridge. It was developed in 1988 by Evan Whildin of Action Arms. The Magnum Research Desert Eagle was the first handgun chambered for the .50 AE. Among the few commercial handgun cartridges designed that exceed its ballistic performance are the .454 Casull, .460 S&W Magnum and the .500 S&W Magnum.
500 S&W Magnum: The .500 S&W Magnum is a cartridge that was developed by CorBon for Smith & Wesson for use in their Model 500 revolvers and introduced in February 2003 at the SHOT trade show. It is the most powerful handgun cartridge commercially manufactured with over 2500 ft·lbf (3.5 kJ) of energy created with a 440gr bullet travelling at 1625 fps. Some loadings can even achieve muzzle velocities of 2300 fps using a 325 grain bullet. This produces a muzzle energy of over 3817 ft·lbf.