Still under construction, but check some of these tips and web sites out.
You can usually get decent ticket price if you fly on special days, like Saturdays and return during the week. Try to avoid traveling on the days that everyone else travels on. Take an extra day off of work, it might save you $100 on an airline ticket. You also helps avoid the traffic.
Another tip is to find an airline that frequently flys to your city or uses your city as a hub. Their ticket prices are going to be cheaper than an airline that doesn't fly so often to your city of departure.
Travelocity This site can usually get you the cheapest tickets. They also send you updates via email. Just put in a couple of destinations, and when the price changes, they send you an email.
American Airlines They have some great weekend deals if you want to go from one major city to another. Eventually you can check out my trip over labor day weekend from Austin, TX to Madison, WI. It cost $188 round trip. We had to leave on the Saturday and return on that Tuesday. Which if you have a flexible job, isn't a problem.
There are plenty of others. Check the others out too, if you have time. But I think Travelocity can find the best deals and American Airlines some great last minute deals (last minute being about 2 weeks ahead of travel). Other airlines usually match prices, but American Airlines has extensive routes and a pretty good service.