Check out this new website.
http://www.wolframalpha.com/
The site was just launched recently, and seems to improve daily. It is basically a logic-based search engine. I'm a Math Science major so it helps me out greatly. Type in any equation, and it can possibly lead you through it. I have seen it fail, but usually it is perfectly accurate. I'm sure the bugs will be worked out over time. It does other things too