Wolfram|Alpha

Seriously, check this site out. If this was around back when I was doing undergraduate math or even back in high school, I'd get perfect scores for all my homework and assignments. Seriously.

http://www.wolframalpha.com/examples/Integrals.html

There's so much more that the site can do than just math. I suggest you go and see for yourself.

I am such a geek.