• Orbitz is our go-to for flights across the country or even transatlantic ones. We've consistently gotten good deals as long as we book about 2 weeks in advance. We even got a cheaper fare on Virgin America going from LA to New York on Orbitz than was listed on the Virgin America website.
• Priceline (yeah the ads with William Shatner, hilarious!) works a little differently than Orbitz and other online flight finders. On Priceline, you name your price for a particular trip and then if the airline accepts your offer, the flight is booked, and you cannot get out of it (trust us we tried once). You can set the time of day you'd like to leave and how many layovers you're willing to have. But they don't reveal the details until once the trip is booked. We got an incredibly cheap fare going to Oregon this way, but it was definitely a little stressful.
• Hotwire let's you choose an area to stay in and the caliber of hotel you'd like (4 stars, baby!) and then they show you some options without revealing the exact hotel or location until after you book it. This is our go-to for last minute bookings since it has turned out to be infinitely cheaper than booking directly through a hotel. Of course this only works if you're flexible about where you're staying. You can't search for a particular hotel and try to find a deal.
• Travel Zoo sends out a weekly email with 20 great travel deals ranging from cheap airfare, a great 4 star resort or even cruises. We make sure to check each week since sometimes deals are so good, you can't pass them up. (Our old neighbors booked roundtrip plane tickets to Chicago from LA for $20).
There are a milion other sites out there, but we've had luck with these so we're sticking with them. Care to share where you find great deals?