Wolfram|Alpha
<http://www.wolframalpha.com/>
This new "answer engine" has been available for just over a month. If
you haven't heard of it, here's a brief overview.
Wolfram|Alpha's long-term goal is "to make all systematic knowledge
immediately computable and accessible to everyone. We aim to collect
and curate all objective data; implement every known model, method,
and algorithm; and make it possible to compute whatever can be computed
about anything."
The site has more info, including videos and examples:
* Examples by Topic
<http://www.wolframalpha.com/examples/>
* Visual Gallery of Examples
<http://www.wolframalpha.com/gallery.html>
It's not just for serious questions, though:
* Top 10 Wolfram Alpha Easter Eggs
<http://mashable.com/2009/05/17/wolfram-easter-eggs/>
* 10 Even Better Wolfram Alpha Easter Eggs
<http://mashable.com/2009/05/17/better-wolfram-easter-eggs/>
For example, Wolfram|Alpha answers its own age when asked:
<http://www.wolframalpha.com/input/?i=How+old+are+you%3F>
