Wiinput

Wiinput is a free utility for Windows XP, Windows Vista and Windows 7 that allows you to use the wireless remotes that come with your Nintendo Wii console to control games and applications on your computer.
Configuration files are used to define what Wiimote events to capture and what actions to execute when those occur.

A number of premade configurations come included with the software. For example, there are some to control the mouse in different ways, one to control Google Earth and one to use the Guitar Hero controller with the open source game Frets on Fire.
An interactive editor that will allow anyone to create custom configurations is currently under development.