How about the ones that aren't anymore....
Piedmont
PSA (Pacific Southwest - bought and shut down by US)
Western (bought by DL, and essentially shut down)
Malaysia Singapore Airlines/way (split to become SQ and MH)
British Overseas Airways Corp.
British European Airways (both merged by U.K. govet. to form BA)
Dan Air
Pacific Western
CP Air/Canadian Pacific/Canadian Airlines ("acquired" by AC)
Reno Air (acquired by AA)
Swiss Air
Sabena
Air Liberte (under BA)
Pan Am
TW (Express at any rate)
Might be a few I forgot about