shows several bases of a number simultaneously. It shows 7 edit fields representing decimal, binary, hexadecimal, octal, vinkadecimal, IP address, and 4 character long. As you type in any of these fields, all the other fields are updated.
BaseMaster will also let you do common geeky-math operations on your numbers. Geeky math is things like AND, OR, and XOR. It also does the common arithmentic operations.