For you Late to the party people:
AR
http://www.botachtactical.com/magpulpmag.html
($13 P mags)
AK
http://www.classicarms.us/
($10)
Hk... I don't know if it's ongoing...
http://www.robertrtg.com/g3magazinensurplus.html
M1A (You can backorder)
http://www.44mag.com/prodinfo.asp?number=CM20
AR
http://www.botachtactical.com/magpulpmag.html
($13 P mags)
AK
http://www.classicarms.us/
($10)
Hk... I don't know if it's ongoing...
http://www.robertrtg.com/g3magazinensurplus.html
M1A (You can backorder)
http://www.44mag.com/prodinfo.asp?number=CM20