Originally Posted by haubd

Well, let's see:

Domestic:
CO DEN - Denver
CT HVN - New Haven
DC IAD - Washington Dulles
FL MCO - Orlando
IL ORD - Chicago
MA BOS - Boston
MD BWI - Baltimore
MI DTW - Detroit
MI LAN - Lansing
NM ABQ - Albuquerque
NY ALB - Albany
NY LGA - New York LaGuardia
PA PHL - Philadelphia
PA PIT - Pittsburgh
TX CLL - College Station
TX DFW - Dallas/Ft. Worth
TX IAH - Houston Intercontinental
TX SAT - San Antonio
SC CLT - Charlotte
UT SLC - Salt Lake City
WA SEA - Seattle/Tacoma
WY CPR - Casper
WY JAC - Jackson Hole

International:

ESB - Ankara
IST - Istanbul
PMI - Palma de Mallorca
AGP - Malaga
IBZ - Ibiza
MLA - Malta
FRA - Frankfurt, Germany
PRG - Praha, Czech Republic
LHR + LGW - London, UK
YHZ - Halifax, Canada
YUL - Montreal, Canada
YYZ - Toronto, Canada
MEX - Mexico City
LCA - Larnaca, Cyprus

Only 23 (and 15 International)...

And some that probably don't count (Train stations)

BNJ - Bonn, Germany
QKL - Cologne, Germany

Favorites

Least: DFW
Most: SEA