Broadly speaking, if you can't play it in iTunes, you can't play it on your iPad. You'll either need to convert it first, or use an app/website that converts it on the fly. I don't know of any off-hand, but one way or another, you're gonna have to convert it. Edited by Moderator - no twitter links, please read the forum rules
AV player HD and VLC both play avi files brilliantly. Download and access in File sharing in iTunes. Just add your avi files to the app in file sharing and it will copy them to your iPad.
Azul is another player that plays almost any video format. It doesn't need to convert them to a standard format either.
I have looked at AV Player HD which appears to be available as an app for Ipad2 but not for the iMac. However, the app's short description of itself does not list the files that make up the video I have. The video I have was made with a Windows PC program called Roxio 8. The files on that movie video have extensions of VOB, IFO, and BUP. Does anyone know if AV Player HD handles movie video files with those extensions? As far as I understand (which is very little) AV Player HD loads only onto the iPad 2 and not onto my iMac (or for that matter onto my Windows PC). So secondly, if that is true, how do I get the movie video onto the iPad? Again, any help is greatly appreciated.