For iPhone to mac transfer of any file (pic, music, video...), use the iPhonedrive software($9).
For iTunes' library transfer from a Mac to another Mac, get the movies directly in their folder in the iTunes' music folder. Copy them on a DVD for transfer, or if they're in the same room, use the Target mode to connect them through their firewire ports for direct transfer.
You can also access one Mac from the other using network/sharing. Or if you have a .mac account, put the movies in the public folder of you iDisk and any computer can download them.