Don't forget priceline Bob. People can name some outlandishly low price, and often get it. Folks, give priceline a try. Read the disclaimers closely, but I've used this service several times to obtain incredible rates. I've flown to DC a number of times for $200 round trip. Try entering that price with priceline for a round trip, or even lower depending, and see what you come up with. Be prepared to travel if they can meet your price!
http://www.priceline.com
Hotwire is pretty good too. And you can see the price before you buy.
HOTWIRE
I even got bumped up to first class once on a hotwire ticket. Talk about bargin!