I'm a huge fan of gadgets which have the possibility of open source third party updates. I have a couple of Linksys routers that I've reflashed with DDWRT and/or Tomato and/or OpenWRT. I've played with the NSLU2. I have a Canon SD1100 which I run CHDK.
Today, I discovered another interesting one:
This is firmware for the Canon 5D Mark II DSLR to adapt it to the specific needs of film makers. While the 5D is nominally intended as a still camera, it has many advantages when compared to equivalently priced setups when used as a motion picture camera. This firmware is designed to expand this use considerably. Very cool.