Airline Sites:
http://beta.itasoftware.com/ (Best place to check fares
http://www.usair.com/ (hometown carrier)
http://www.nwa.com/ (Cheap to Europe during sales)
http://www.aa.com/
http://www.jetblue.com/ (Best airline ever)
http://www.delta.com/

Useful Airfare Sites:
http://www.kayak.com/ (Newly Added)
http://www.mobissimo.com/ (Newly Added)
http://www.bestfares.com/travel/desks/desk.asp?desk=news (Subscriber-based cheap fares)
http://www.orbitz.com/ (Monopolistic Site that works well)
http://www.farechase.com/ (Not bad)
http://www.air-fare.com/ (find lowest published fares for US city pairs)

Other Airfare Sites:
ITN/AmEx
http://www.iecc.com/airline/ (Wonderful info)
http://home.netcom.com/~rcowen/ (A guy who knows his travel)
http://www.terrytrippler.com/ (Airline Information)
http://www.qixo.com/ (Funny Name)
http://www.airfare.com/ (Not bad)
http://www.airsaver.com/
http://www.statravel.com/ (students only)
http://www.economytravel.com/

French Airfare Sites:
opodo
Anyway
eBookers
GoVoyages
Travelprice
Travelonweb

Airline Related Sites:
https://www.checkmytrip.net/ (check your own flight plan!)
http://www.trip.com/ (for in-flight monitoring)
Find the closest airport
http://www.virtuallythere.com