, which does compare prices from all the major airline sites, other discount sites, and jetblue, frontier, and others who don't show up on expedia and travelocity.
I just found a boatload of American Airlines roundtrips NYC-SLC out of LaGuardia for $206 3/22-3/29 without trying hard. When I was commuting out here from Boston I often found that American was way cheaper than others. Since they do not have any nonstop service to Denver or Salt Lake from the east coast (everone connects in Chicago or Dallas), they tend to undercut a lot of fares from the airlines that do fly nonstop (Delta, Frontier, etc.) Looks like Continental and Delta have pricing in that range too as long as you're willing to make a connection.
Granted you'll be flying the "Greyhound bus of the skies" on American, (a "Maddog" Super-80) but on the other hand they have a real frequent flyer program too. Southwest and Jetblue get a lot of people flying them without checking the "majors" because they just assume that they're cheaper - and often they are not. Back in the day (as in 2004) JetBlue had a bunch of really good deals - but they've crept up quite a bit. And they're now the last of all US airlines in on-time performance. Sad.