I use itasoftware's beta site all the time. They aren't perfect because the data is not real time. But, they're close enough to get the general gist of things.

I find that the "300 mile" feature is especially helpful - with five searches (LAS, OAK, SLC, PDX, DEN), I can cover all of the AA last-minute one-way fares from ORD west, then either connect them with a cheap HP/AS/WN flight or drive 100 miles to get to my destination for a mid-week trip. Same thing for the Northeast corridor - 300 miles from PIT, HPN, and RIC pretty much covers everything.

I figure that I've saved our company $2000 on airfare this year from info from their site, while still staying on AA for the vast majority of my miles.