It's an incredibly fun plaything for geeky people like me, but also educational. I'm learning Python, and I have mine always running and set up so I can ssh to it anywhere from my cellphone. I fire up emacs through ssh and work on my Python programs when I'm commuting by bus or train. I also have it set up with CLISP and Scheme for when I want to mess around with those.

But the funnest thing is that I used samba to mount the music directory on my desktop, so that I can ssh in and play music from my cellphone from anywhere (it's connected to the speakers and TV in my living room). I also use it to play videos from the video library on my desktop.