Secure copy a movie from Mac to iPad
If you want to watch with the built in iTunes Player, I would suggest Music2iPod, a free app that can access any file (including videos) on a jailbroken iDevice and add it to the iTunes library. To add the video file to your device I would suggest connecting with a GUI SCP program (like Cyberduck) and transferring to the default directory (it really doesn't matter where, as long as you have read/write access and can remember it), then navigating to this with Music2iPod, which will then add the video to your iPod library for you.