I don't know much about Wolfram Alpha except that its developer Stephen Wolfram is well known in the mathematical community as a ground breaking thinker.
His business is based on the Mathematica software package and he has written a book called A New Kind of Science about a way of approaching science that is closely related to fractal analysis and artificial intelligence.
Wolfram Alpha appears to be a Google like interface that will actually answer questions!
Coming in May 2009....we'll have to wait and see how well it works...
Announcement from Wolfram Research website