Google Calculator

www.google.com has become more then just a search engine. It is a phone book, it looks up local movies, it looks up stock quotes, it can tell you the weather, and more. One thing that I thought was interesting was that it can be used as a calculator and can perform conversions between different units.

Example
- 1 + 1 in hex
- 10 + 10 in roman numerals
- 1 metric ton in ton
- 5 cubits in feet
- 20 degrees Celsius in Fahrenheit
- 30 degrees C in F
- 6 fortnights
- 6 fortnights in weeks
- pi + 10 / 2
- 100 miles in kilometers
- 0b1100101*0b1001 (Binary math)
- 0x7f + 0x7f (Hexadecimal math)

I can't seem to find a full list of valid units, but it does seem to support quite a lot.

Also, google has patent searches (http://www.google.com/patents), source code searches (http://www.google.com/codesearch), and blog searches (http://blogsearch.google.com/).