I use Google and Bing.
While Google is great at a lot of things, they sometimes screw things up (the new Google Maps, for example). Bing is similar enough to Google, so if a Google product fails, I just use its Bing equivalent.
Also, I like looking up the randomized news on Bing's homepage. They post interesting stories there quite often. I'm also signed up for Bing Rewards and get free gift certificates once in a while.