Let's see here... In no particular order:
AA/Eagle
TWA/TWE (RIP
-- recently found my Aviators Elite card)
DL/Shuttle/ASA/ComAir
AeroFlot (both in the Communist days and more recently)
AirFrance
BA
CO
NWA
Alaska/Horizon
USAir/Piedmont
AeroSvit operated by ARP 410 Airlines
United Shuttle
AeroMexico
Hmm... pretty short list when compared with some of the others.