Moon Buggy?
Well seriously, apart from the latest fast paced action games... here are some ideas:
- Router/Firewall - Basically, this way you've got full control over things like traffic prioritisation, rate limiting and the like. With a little fiddling you can still read webpages when your housemate has his Bittorrent going, for example.
- Fileserver - Its surprisingly trivial to set up RAID, and it makes a nice place to keep your photos, music, movies, and things. Share your music to iTunes with mt-daapd, watch your videos on a slightly hacked Xbox and store your documents centrally with Samba. Use SCP to get your files when you're out.
- Kai - Run a Xlink Kai gateway. Play games over the 'net with a PSP, Xbox (without Live), Xbox360 (without Live), PS2, or Gamecube! (OK, you don't actually need Linux for this - it works on Windows too - but that is not as cool
)
- Asterisk - Get your PC to answer the phone when you're out, take a message and email it to you. *Note, requires muchos patience and determination to get working*.
- About a zillion other things....