Very unofficial list, which may or may not be current or factually correct. Others can chime in.
Delta - ATL
UAL - ORD
American - DFW
US Airways - PIT (last I knew, could be PHX???)
JBU - NYC (talk of moving to MCO)
Air Tran - MCO
SWA - DAL
Spirit - Miramar, FL (MIA/FLL)
Republic/Frontier - IND
Skywest - SGU
Mesa - PHX
PCL - MEM
Compass - MSP
Mesaba - MSP
Express Jet - IAH
Great Lakes - DEN?
Gulfstream - FLL