Wolfram Alpha will provide an API for accessing data.

According to information received by the guardian.co.uk employee from Conrad Wolfram (Conrad Wolfram, creator of Wolfram Alpha), an unusual search engine for technical and scientific information will soon provide an API to access its data. Currently, Wolfram Alpha users can access information only through a website or a plugin to the Mathematica package. But soon, anyone can use the API to get the results and use them in their development.

via www.guardian.co.uk/news/datablog/2009/aug/28/searchengines-internet