Magic Lantern: a filmmaker-friendly firmware replacement for the Canon 5D Mark II
Magic Lantern firmware introduction (Thanks, Trammell!)
I've released a custom firmware for the Canon 5D Mark II that adds lots of new features that are missing for film makers. The video mode on the camera is an amazing step forward for independent films -- it has a full 35 mm sensor for "film-like" depth of field, it works with any Canon EF lens and it produces beautiful 1080p h.264 files at 50 mbps.
But the stock firmware has limited audio support and is missing many key features. So I wrote my own extensions that include onscreen stereo audio meters, over-exposure displays, crop marks for different formats, and higher-quality audio.
After a few weeks of private alpha testing and evaluation, I have released it under the GPL for other folks to be able to extend it further.
(If you don't have a 5D, check out CHDK for Canon's point-and-shoot cameras. It provides pro-level features for their low-end cameras, including a scripting language!)