As a frequent traveler (I have a tendency to hop onto a plane every 3 months or so and go somewhere, usually the east coast), I'm always looking out for great deals. Frequent flyer miles are something awesome to rack up (which reminds me, I really should sign up).
When looking for an airline ticket, Its always good to use multiple sources. I have found that expedia and orbitz tend to give the same results. I have recenlty discovered farecast.com. This website is better than Orbitz or Expeida (which I'm used to using) in that it searches all of those budget websites and finds the best deal out of all of them. One of the features that I find helpful is the "time grid"
As you can see, it gives you the TOTAL price it would cost if you left early morning and late afternoon, etc and all of your different time possiblities. This helps at a glance if you were debating between early morning or red eye.
For those with a thin wallet, farecast will also provide a grid of the airline prices and also pojects if the prices for a certian ticket will go up or down.
another great thing about this site is that it shows you right off the bat the price of the entire trip, verus some sites which give you the price per ticket, vs the round trip price (which can be shocking to find at the end).
one thing that i did not find easy to use was the sliders on the side options in which you can change your perfered arrival/departure time and the min and max prices. It does a realtime update (read: everytime you slide it to a new position, it updates the website), and i find it rather tedious, espeically if you have a slow running computer.
happy hunting ladies and gentleman!