Great idea for a thread....
Carriers:
Comair-commuted on these guys for years. (looking back through my N-numbers, I had actually been on the LEX accident aircraft (431CA) a few years before)
ASA-(now part of ExpressJet)
Colgan AIr-both on the Saab and Q400. Never got to ride on the Beech.
Freedom Airlines (the DL Connection system, was part of Mesa Air Group), both DHC-8 and E145
MetroJet (US Airways, single-class B737-200's)
Southeast Airlines (MD-88, charter)
When I worked the ramp, I threw a lot of bags into USA3000's A320's.....also worked Ryan International frequently.