There's travelocity.com, cheaptickets.com, travelation.com, expedia.com and several more. So what you basically need to do is compare them all. Search for the flight you need on each of these travel websites, and pinpoint the best current deal.
It's a bit of a pain, but doesn't take too long. Then there's the time issue. When you research airline ticket purchases is always crucial. One day can make a huge difference.
I was shocked to see a 400 dollar plane ticket skyrocket to 670 overnight. As ridiculous as this sounds, it's still our reality.
Any time you choose to fly, remember to arrive a couple hours early. Chances are you'll be the one that gets heavily searched at the security check, and then be held up for a good amount of time. You don't want to miss your flight!