Arstechnica is reporting that the latest iPods and iPhone are actually capable of video resolutions up to 720×576, this is a much better resolution than 640×480 and is coincidentally the same maximum resolution as PAL DVDs.
I had actually noticed before that the rented iTunes movie files were at resolutions such as 853×366 (Fantastic Four has a similar resolution but I can’t think of exactly what the numbers are) but I didn’t do any more research on the matter.
Arstechnica also points out that these 720×576 resolution video files have to be at 25 frames per second and done with H.264 baseline encoding, but once encoded they can be either synced to the iPod/iPhone through iTunes or with the iPod Touch and iPhone viewed using MobileSafari.