You can use the old AV cable or an S-Video cable with the old iPod Universal Dock and get video out from the 3G nano and the classic but not just plugged into the iPod itself.
Apple has a Knowledge Base article showing the different configurations that work with new and old iPods.
The gist:
Old Universal Dock + AV cable = Yes
Old Universal Dock + S-Video cable = Yes
New composite cable = Yes (3G, classic, 5G iPod)
New component cable = Yes (3G, classic), No (5G iPod)
Here's the article:
Apple KB Article about TV Out support.