• Web Server
• Media Server
• Paper weight
• DVR (put a TV Tuner in it) -- nah, probably not enough processing power unless the GPU takes over
• Classic arcade game/ Classic video game console emulators (think MAME).
• Heater for really cold nights (just remove the heat sink and fan).
• "Car"puter -- somehow jam it into the dash of a car, like where the passenger side airbag should be.