The supported video format for an iPod is MPEG-4 (max 2.5Mbps, max 640×480, simple profile) and H.264 (max 1.5Mbps, max 640×480, baseline profile only), and the resolution of the 2.5” iPod display is 320×240 pixels (it is capable of outputting 640×480 via the optional AV cable). Well, chances are you don’t have either of these formats lying around - even though those DivX and XVid's technically are MPEG-4 part II implementations, they belong to the Advanced Simple Profile, which the iPod is not capable of displaying. Now one solutions is to download the videos from a sites such as YouTube, Google Video or Daily Motion - this can be accomplished using the excellent Firefox plugin VideoDownloader. To convert to the iPod format, I use Videora iPod converter. It is also possible to rip dvd’s and convert them to iPod format. Handbrake converts to iPod format in excellent quality - but is not able to remove the CSS encryption - so either rip the DVD’s with DVD Shrink or install DVD43 which transparently removes the CSS encryption from any DVD inserted. Also notice that Google Video offers the possible to ‘Download for Video iPod / PSP’ for certain movies (e.g. Pirates of Silicon Valley). Finally, if iTunes doesn’t do it for you, this Comparison of iPod Managers might be helpful.

* Rockbox | An open-source replacement for the Apple iPod OS. Unpolished and with lots of rough edges - but it makes it possible to play Doom in 320×240.