Wolfram|Alpha should have launched officially by the time you read this, though it has been live since Friday evening. The execution is slick. The different result visualizations are a great idea. It’s loaded up with cool widgets and APIs. Most of the time the servers don’t fall over (despite some glaring security holes). To quote FriendFeeder Iddo Friedberg it’s “a free, somewhat simple interface to Mathematica”. Free for personal, non-commercial use, anyway. If you’ve got any questions about the GDP of Singapore then wolframalpha.com is the place to go.