I purchased DVD Catalyst Check out the section for them at the bottom of the Forum listings.
There is also Pavtube Software Studio (I have no direct knowledge on this one.
Both venders support this forum.
The problem with a lot of the software out there that says it can remove DRM from iTunes movies is that it does so by re-encoding the file. You might want to do a little searching on a tool called Requiem, in it's current release it's the first software to remove DRM from iBook purchases. This tool just removes the DRM protection without re-encoding meaning that it is a loss less process. Re-encoding not only takes more time but you will get quality degradation in the process. I've used Requiem successfully in the past when I had an iTunes account so that I could watch my purchased movies on non Apple home media player.
Keep in mind that with Requiem it may stop working if you update iTunes, you may want to check that the latest version of it supports whatever iTunes updates you install. I don't have the links to Requiem but my guess is you'll need to download it via torrent as I don't believe there is an actual home for it.
EDIT: Just found this which should help you get started if you're interested in Requiem: