THIS MAY HURT YOUR CAMERA. IF IT BREAKS YOU GET TO KEEP BOTH PIECES!
Actually the risk of that happening is really small... If you feel like something is wrong with your camera, turn it off and remove the battery.
Magic Lantern 0.2.1 Unified
... for Canon 550D, 60D, 600D, 50D and more
Magic Lantern is a custom firmware add-on for Canon dSLR cameras. It is not a hack, or a modified firmware, but it runs alongside Canon's own firmware, booting from the card every time you turn the camera on. The only modification to the original firmware is the ability to boot software from the card.
Magic Lantern is being developed by both photo and video enthusiasts; its features include manual audio, zebras, focus assist tools, bracketing, motion detection and much more.
Download - Canon 500D (T1i) (ALPHA VERSION)
All the other cameras named above
ALL DOWNLOAD LINKS FOR THE UNIFIED RELEASE
for Canon 5d Mark II