Wolfram Alpha is amazing!! I threw some of the most complicated equations and systems of equations at it when I was getting my physics degree. It not only handles them, it shows the work... Seriously, I'm not sure I'd be able to use the integral chain rule on my own without the repeated solutions offered to me by Wolfram Alpha.

Even better, though, is that you can type in just about anything into the search bar and get a page full of something. Try typing your first name into the search bar, for instance.