Wolfram|Alpha

I've known about Wolfram Alpha for quite some time now, but just noticed that I can put a little bar on my site, so I have one on the right now. Wolfram Alpha is called a computational knowledge engine - it "is the first step in an ambitious, long-term project to make all systematic knowledge immediately computable by anyone," according to the site.

It's really hard to describe, so I recommend trying out instead. There are a few searches they recommend for beginning users, just to get a feel for what it can do, try:

entering any date (e.g. a birth date: june 23, 1988)
enter any city (e.g. a home town: new york)
enter any two stocks (IBM Apple)
enter any calculation ($250 + 15%)
enter any math formula (x^2 sin(x))
enter any two first names (andrew, barbara)
enter any food (1 apple + 2 oranges)
enter any chemical formula (H2SO4)
enter any musical notes (C Eb G C)

You'll probably be surprised at the amount and type of results you get from this engine - it's pretty crazy. Not only does it often give info in a number of different categories, it has more info in each category than it shows at first... just click on the More link in a particular frame.

Have fun!