How can I add movies to my iPad from both my home and work computers?
There used to a be a method where by you edited the iTunes Music Library.xml file on the second computer to make your device think the two computers are the same computer. I'm not sure if it works any more though. Explanation guide here
Alternatively the easier way of doing it is to take advantage of iTunes file sharing and use an application from the app store. The advantage of this is that most app store video playback applications support more file formats than would be supported though the default video playback app so you won't need to do any conversion before copying the videos across.
The application I would recommend, and use myself, is AVPlayerHD