Steam Mover

Steam Mover can be used to move any folder around (by changing the Source Path), but for Steam the maximum benefit is in moving individual games from the Common folder.

Steam Mover was originally designed to help gamers move their downloaded games from the Steam client in order to free up space. It also work well with other application. The program's target directory defaults to the applications folder for Steam, but simply change this to the folder containing the applications you wish to move.