What's a good web app for finding hotel deals and includes real time vacancy data about the hotels? What about one with an API? I'd appreciate any help.
The best hotel deals so far I've found on hotwire.com. They have an API as well. We did use them to plan a road trip while on the road :). I don't believe they offer vacancy data though (of course, this being hotwire, you won't know what hotel you're booking until you've booked it - but no disappointments yet).
If you go to m.hotels.com, they've got a pretty well done mobile site, and they are pretty good for prices, bookings and information.