iTunes 6 allows you to organize the videos you want to sync with your 5G iPod, but unfortunately, it’s a very clumsy implementation of this feature.
Once you get your videos into iTunes, either through buying them from Apple, or ripping your own, they show up under the ‘video’ list item in the left side column. Once you select ‘video’, you get a series of buttons across the top that allow you to sort by Movies, Music Videos, Podcasts, or TV Shows. Unfortunately, your control over how things are classified is very limited.