The project builds a remote control system for a floor fan. Care was taken as to alter the fan itself as little as possible. The main hardware consists of a servo, an IR Receiver, an IR Remote, an Arduino Mini, and a 5V power supply.
The control system is a finite state machine with 4 states (off, speed_1, speed_2, speed_3). The remote is able to switch the fan between those 4 states.
For more details on the construction process, take a look at the wiki page. For an example of the system's performance, there is a short video on YouTube.
The project is also available at codebender.