Wolfram Alpha is a 'computational knowledge engine'. A lot of people got confused and compared it to Google. But its not a search engine. Instead, it compares and contrasts (mainly) numerical data in novel ways, according to questions that you can write in plain English. In other words, as long as your question is phrased in the right way, Wolfram Alpha will understand it and pull together information from disparate sources in order to answer it.
But won't be released until later this year. I'm pretty excited about this new service as I love Gmail.
A direct competitor to google, it seems. Fully launching on June 3rd.