My new favorite flight reservation site is www.hipmunk.com.
Maybe it’s because I’m a visual person, but I find the flight display, all on one page, all on the same timeline way easier to use than the long lists that I get from other sites.
The prices look identical as well. Now, I haven’t actually used hipmunk to make any reservations — and Expedia has come through for me a couple of times when I had problems while on a trip — but I’m definitely going to give them a try and hope their UI skills carry over into their travel service skills.
I tried their hotel reservations as well. It has a great map-based interface, but the selection seems a little slim. I was looking for a place in Mexico City, so maybe they’ve yet to fully populate it. Once they do, it will be my first choice as well.