Wolfram Alpha launched last week and has been touted as a threat to Google, but the comparison isn't appropriate at the moment. Wolfram Alpha is not a search engine (of course, it might become one some day). Instead of drawing on an index of web pages, Wolfram Alpha produces answers by using a managed set of 10 trillion pieces of data and 50,000 algorithms and models.
I have spent a few hours trying out Wolfram Alpha, and my results have been mixed so far. The engine is good at looking at easily-identifiable hard data such as statistics about San Francisco. Feed it something more subjective like, say, Manhattan Project, and you get John Lithgow's 1986 magnum opus instead of the project to develop the first atomic bomb. I expect these results to improve with time.
One very interesting feature I did notice, however, is that Wolfram Alpha does medical computations. Right now the engine can compute blood oxygen level, average blood sugar levels, or even estimated conception and due dates.
For a complete list of Wolfram Alpha's medical capabilities, check out its Health & Medicine example page.