I did a quick GOOGLE search and came across this website.
Not sure where this guy got his definition of a hub, but many on this list are correct while some are wrong for what you are looking for.
I posted the unedited list according to the author so you can decide what is right and wrong.
Also, not sure when this list was compiled, but some of the airlines and cities are outdated these days while other airlines are absent.
http://www.faqs.org/faqs/travel/air/handbook/part2/section-13.html
Airport Abbreviations and Hubs:
ABQ Albuquerque, NM WN
ANC Anchorage, AK AS
ATL Atlanta, GA DL, AT
BNA Nashville, TN AA
BOS Boston, MA NW
BWI Baltimore, MD US
CLE Cleveland, OH CO
CLT Charlotte, NC US
ORD Chicago, IL UA
MDW Chicago, IL WN
CMH Columbus, OH HP
CVG Cincinatti, OH DL
DAL Dallas (Love Field), TX WN
DEN Denver, CO UA
DFW Dallas/Ft. Worth, TX AA DL
DTW Detroit, MI NW
EWR Newark, NJ CO
HOU Houston (Hobby), TX WN
IAD Washington (Dulles), DC UA
IAH Houston (Intercontinental), TX CO
IND Indianapolis, IN US
JFK New York (Kennedy), NY TW DL
LAS Las Vega$ HP
LAX Los Angeles DL US
MEM Memphis, TN NW
MKE Milwaukee, WI NW YX
MSP Minneapolis/St. Paul, MN NW
MSY New Orleans, LA CO
ORD Chicago, IL AA UA
MCO Orlando, FL DL
PHL Philadelphia, PA US
PHX Phoenix, AZ HP WN
PIT Pittsburgh, PA US
RDU Raleigh/Durham, NC AA
SEA Seattle, WA AS UA
SFO San Francisco, CA UA US
SJC San Jose, CA AA
SJU San Juan, PR AA
SLC Salt Lake City, UT DL
STL St. Louis, MO TW
SYR Syracuse, NY US
AA American Airlines
AS Alaska Airlines
AT AirTran
CO Continental Airlines
DL Delta Airlines
HP America West Airlines
TW Trans World Airlines
UA United Airlines
US U S Air
WN Southwest Airlines
YX Midwest Express