Playlistmag.com has done a great job of detailing the latest features added to iTunes 5.0. And, if you have not yet updated to iTunes 5.01, grab the latest version. It has a pile of fixes that make iTunes more stable.
One of the most overlooked features of iTunes is its support for video. There are not a lot of vid-casts out there right now, but the numbers are growing.
Checkout the rundown on the new iTunes features at Playlistmag.com. And, for a running list of the latest vid-casts out there, checkout VidCast.org. You can subscribe to a vid-cast through iTunes just like you do a podcast. But rather than listing to the potcast, you can watch it as well.