Wolfram|Alpha

For those of you who don't know it, Wolfram Alpha is a very powerful online engine designed to answer your questions. Unlike normal search engines, Wolfram Alpha processes your question and attempts to answer by computing from structured data, whereas a normal search engine would just provide a list of documents or web pages that might contain the answer.

Wolfram Alpha always manages to astound me with its profound accuracy and precision.
The cool thing is, wolfram is not limited to science- or maths-based queries.


Wolfram Alpha can also respond to increasingly complex, natural-language fact-based questions such as:
 "Who is Robinson Crusoe?"
"How old was (someone) in (year)?"

Also, one can input the name of a website, and it will return relevant information about the site, including its hosting location, site rank, number of visitors and more. I just knew this recently.

More information:
http://www.wolframalpha.com/about.html

From wikipedia:
The following are examples of queries using Wolfram Alpha. They are accompanied by links to the results of each search to illustrate the variety of answers that Wolfram Alpha provides to non-specific queries.

• mortgage 6%, 25 year, $140000^[8] displays, among other things, repayment rates and graphs that represent capital vs. interest over time.
• life expectancy france 25 year old male^[9] which gives a survival analysis for a person of the given demographic.
• boiling point of water at 6 atm^[10] which returns a phase diagram alongside the result of 432.6 Kelvins.
• lim(x->0) x/sin x^[11] yields the expected result, 1, a plot, and the series expansion. The button "show steps" provides a possible derivation of the result using L'Hôpital's rule.^[12]