http://www.mathsisfun.com/combinatorics/combinations-permutations-calculator.html

For statistics borap like me.

http://www.mygeoposition.com/

Useful for finding the latitude and longitude of an area.

http://www.softwareprojects.com/resources/programming/t-mysql-storage-engines-1470.html

Useful when deciding which storage engine to use in MySQL.

http://www.daftlogic.com/projects-google-maps-distance-calculator.htm

Useful when trying to find out the distance between places.

http://jarlsberg.appspot.com/

Very informative site to learn different exploits and how to defend against them.

http://nuthatch.com/kanjicards/

A very awesome site for studying common Japanese Kanji.