If you have a stack of XVIDs, MKVs or WMVs as i do and you want to watch them on your iPad, then you can easily do this by purchasing the GPlayer App for £1.99 (or free if and when you jailbreak your device).
When the App is on your device, open iTunes, if not already open, click on your device in the DEVICES menu on the left hand side, choose Apps from the breadcrumb ribbon at the top, scroll to the bottom and find GPlayer in the File Sharing list, click GPlayer and then click on Add... then browse to your .avi, .wmv or .mkv (latter on iPad2 only) and then sync. The file will be played through the GPlayer app on your iPad. Simple.
Obviously, streaming the movie from your PC/MAC would be a whole lot easier but that's a different tut!
Click Apps at the top of the screen: :)
Click on GPlayer at the foot and then Add... your movie(s), then Sync.
