Stephen Wolfram, the creator of Mathematica, is about to launch Wolfram Research's latest (and most ambitious) creation, Wolfram|Alpha. It will probably revolutionize how you find information on the Internet — and what kind of information you can find. Actually, "find" isn't the right term. It's far more than searching and finding, it's computing, categorizing, comparing, organizing …
It's a bit hard to explain Wolfram|Alpha briefly. Wolfram calls it a "computational knowledge engine" and provided a pretty good description in a March blog post.
But seeing it demonstrated is the best way to understand what it does and how far beyond ordinary search tools it goes. If you have 13 minutes to spare (a high-speed connection helps), check out this introduction by Wolfram himself. I was blown away, and I can't wait to start using it.
UPDATE: Wolfram|Alpha is online! But it's pretty slow, and the "exceeded maximum test load" error messages are pretty frequent (and funny: "I'm sorry, Dave, I'm afraid I can't do that"). I guess their 10,000 processor cores are getting hammered.
So it's not at the "blow you away" stage yet, but you can still have fun with it. Did you know that the mass of the sun is 42,947 times the mass of the planets?
UPDATE 2: I've already submitted my first bit of feedback (they solicit feedback on every query result page). If you query "colorado," it reports lots of interesting information about the state, including the population as of 2006 (4.753 million) and the population density as of 2000 (41.5 people per mi2). But it also reports the state's area (104,000 mi2), which I don't believe has changed since Colorado became a state in 1876, and certainly didn't change from 2000 to 2006. So it's trivially simple for Wolfram|Alpha to calculate the 2006 population density (population/area = 45.7) instead of reporting the out-of-date 2000 number it found by searching. Oops.