How to Build a Serial Port Infrared Receiver

This comprehensive guide allows you to control your computer with a simple remote, like the one you already use for your TV-set. It’s very useful when you want to control a DVD or an mp3 player remotely. If you need infrared LED emitters, you can pick up 20 for $3.99.

Don’t miss HacknMod’s communicating using infrared LEDs tutorial.
There’s plenty of software you can install to control this ciruit; for Linux you can use Lirc and for Windows you can use either Winlirc, Girder, IR Assistant or uIRC.