Stephen Wolfram has brought us Mathematica and A New Kind of Science. Next month he promises to bring us Wolfram|Alpha, a "computational knowledge engine" for the web.
Click here for his blog post about it.
Click here for a news article about Wolfram|Alpha.
UPDATE 4/13/09: Another news article about Wolfram|Alpha.
NOTE: Stephen Wolfram is another interesting person who, like Freeman Dyson, intersected with Richard Feynman. Wolfram earned his PhD in physics from Caltech in 1979 at the age of 20, and was on the faculty there 1980-1982. Feynman was at Caltech from 1950 until his death in 1988. Wolfram and Feynman also collaborated in the late 1980s on the Connection Machine being developed by W. Daniel Hillis. (Feynman's son Carl also worked on this project.)
Perfectly Reasonable Deviations From the Beaten Track (2005) is a collection of Feynman's letters compiled by his daughter, Michelle Feynman. In it is a letter of recommendation that Feynman wrote in support of a MacArthur Foundation Prize Fellow Award for Wolfram. Wolfram won the award (commonly known as the Genius Award) in 1981, the first year of the award. The book also includes a 1985 exchange between Wolfram and Feynman about Wolfram's idea to create his own institute to support his research. Feynman recommended against the idea, but Wolfram went on to create the successful company Wolfram Research.
I heard Dr. Wolfram speak at UVM in 2005 and 2007.