One more thing: "Digital Copy" movies are usually DRMed, so you will not be able to convert them with standard software.
If you have iTunes videos, a program called Requiem can remove the DRM so you can watch your videos on your device (iTunes native video format is also the native format of Android).
If your videos are Windows Media Versions, you'll need a different program (which also works flawlessly with iTunes.). However, this program is NOT free. It is called Tunebite Platinum. I think it runs aroudn $29.95 or so. You'll need a good CPU and video card for the best quality conversions, but it does a great job.
One caveat for iTunes (not sure about WM), the Aspect Ratio(AR) is NOT the correct number of pixels that are displayed. So a video might be physically 720X360, but the AR says play at 2.4:1, so the video is stretched to 854X360. I can't find a single player for Android that reads and reacts to AR, so the videos encoded like this play back squished, and I have to re-encode them to be physically 854X360 for them to look correct on my android. Tunebite again fixes this without me having to do a single thing.
Long story short, Android has a way to go to be 100% ready for prime time in the video department, so use Tunebite and save yourself a lot of headaches.