a couple thoughts
1) 3 - 5 min clips are ideal
2) use the "annotations" functionality of YouTube to ad clickable links within the video (ie to the SGU homepage, sources, etc)
3) ive never made a podcast so i dont know the limitations/capabilities, but it would be cool to have pics about the associated topics come up on your ipod. i think astronomy cast tried this early on in their efforts (unfortunately they scrapped it). i dont have a video ipod, so i dont know how theirs looked. but i do think it would enhance the podcast experience. not full video, but just snapshots of relevant images.
4) youtube vids of live interviews at TAM or other engagements would be cool. or if you all go on another field trip to a psychic fair, document the proceedings and post a vid.