How to transcode video for iPod, iPhone, PSP, PDA, or other portable devices. There are a lot of different ways to transcode video for use on portable devices, both automated and manually.
nuvexport is a utility that can be run from the commandline. You select the output format, the videos you'd like to transcode, and it does it for you. It does not automatically transcode for you, however
mythTV can automatically transcode videos after recording them using mythtranscode. It can only transcode to RTJPEG and MPEG4, however, which may not be what your device requires.
Transcoding video to 3gp format for mobile phones
a perl script that can be installed as a User-Job to automatically transcode video for the iPod. May work for other portable devices as well.