This shouldn’t need an internet search but alas, it did.
If you want to download a video that you made with your ipod touch onto your mac:
connect ipod touch
open Image Capture (Apple software included on your Mac)
If you click on your device Image Capture displays all the videos you made and allows you to choose where to download them.
Thanks to Matthew Moore http://www.youtube.com/watch?v=iyI97qjBfqQ
Apparently you can try iPhoto also.