Hack a Day reports a user under the name of [dataghost] has made a firmware hack that adds limited movie recording support to the Canon EOS 40D dSLR camera! There are still some problems though but it's a nice proof of concept.
While [DataGhost] has a working proof of concept he notes that there are still some issues pertaining to the camera powering down while recording a video, autofocusing, and writing to the memory card. Aside from this, [DataGhost] has made considerable progress and is considering adding custom user settings via the mode dial to really give some creative control. We’re excited about this hack and can’t wait for its release to the general public.