One of the first AppleTV hacks to surface was a hard drive upgrade. With the tiny 40Gb drive, I quickly ran out of space and considered doing it myself. A 160Gb drive from newegg.com runs about $100-120 and it looks like it'd take a few hours to do it yourself. I've been looking for an upgrade kit and was pleased to see that Weaknees, the TiVo upgrade people, are selling a pre-formatted 160Gb drive for $199 that is a drop-in install.
I placed an order for one this morning and I'll share some photos of the install and my experiences with it sometime next week. It'll be nice to have room for instant access to every photo I've taken in the past five years, every song, movie, TV show, and podcast I've downloaded.