I generally use Expedia or Kayak, but I'm trying to branch out because I think the content is the same there and I am looking for more unique offerings.
Which brings me to this - there are these new ones popping up that seem to have even more content and rooms. I was using Room77 which is a pretty nice site with extra features and offers a virtual concierge. Then I looked around at AllTheRooms, which actually seems to have hotels, vacation rentals like AirBNB, even hostels and Europe-specific travel hotel sites. It's like I have too many choices and don't know where to go first, you know?
Anyway I'm curious what everyone else uses. I'm researching how I'm going to book stays on the fly as I travel across the country in December.