mathwizz.com

Currency converter
This links to the fxtop.com currency converter. It is available in 11 different languages.

PDF Converter
Good for converting PDF files to Word which may come in handy for doing math homework.

Farhenheit/Celcius temperature converter
You put in the temperature and choose which way you want to convert.

Distance converter
This is what you use if you want to convert miles to kilometres or millimetres to inches or some other Imperial/metric distance conversion.

Area converter
Use this one if you want to convert square feet to square metres or hectares to acres or vice versa.

Volume converter
Good for either solids or liquids, you can convert cubic feet to cubic metres or gallons to litres or fluid ounces to millilitres or go the other way.

Weight converter
Use this one to convert pounds to kilograms or ounces to grams or vice versa.

Degrees/radians converter
Use this one to convert degrees to radians or vice versa.

Computer number converter
You can convert decimal numbers to binary, octal, hexadecimal or vice versa.

A couple of other sites that also do conversions are CalculateMe.com and ConversionTable.org.