www.wolframalpha.com
An amazing site lots of you will find helpful.
Its still under development, but an alpha test version got released about a month ago.
Its kind of a scientific search-engine.
I searched for it on this forum and was surprised it was never mentioned before.
some examples:
http://www33.wolframalpha.com/input/?i=iss
http://www33.wolframalpha.com/input/...s%2C+8e7+m%2Fs
http://www33.wolframalpha.com/input/...n+energy+435nm
http://www33.wolframalpha.com/input/...entaenoic+acid