Andrew, I built an S600. It is considered by many to be the best homebrew out there. It is also the most difficult to "hack" or modify. The greatest expense in a homebrew is usually the camera. Most of the models used are discontinued so you have to find them on ebay, craigslist, or in pawn shops. Depending on what you pay for the actual camera, you can usually build one for less than $150.00. If you decide to do an S600, I recommend that you send it to someone who has done an S600 for the hack. After that part is done the rest of it is fairly easy. If you want to start out with something a little easier, I would suggest a Sony P41. They take excellent pics and if you use the right control board, they can be hacked without any soldering.

Blessings.....Pastorjim