on may 18th, 2009, Wolfram|Alpha has been launched. in contrast to search engines such as google, it is called an "answer engine", a growing knowledge base of structured data. users are welcomed to contribute by submitting specific facts, a whole set of structured data as well as algorithms (http://www.wolframalpha.com/participate/participate.html)
"Our goal is to build on the achievements of science and other systematizations of knowledge to provide a single source that can be relied on by everyone for definitive answers to factual queries." (http://www.wolframalpha.com/about.html)
these sources can be accessed at the bottom of every query result.
at the moment, wolfram alpha "contains 10+ trillion of pieces of data, 50,000+ types of algorithms and models, and linguistic capabilities for 1000+ domains. Built with Mathematica—which is itself the result of more than 20 years of development at Wolfram Research—Wolfram|Alpha's core code base now exceeds 5 million lines of symbolic Mathematica code. Running on supercomputer-class compute clusters, Wolfram|Alpha makes extensive use of the latest generation of web and parallel computing technologies, including webMathematica and gridMathematica."