I recently sampled more iPod accessories than I could fit into a print article on the topic, so consider this blog post an online addendum:
iFlip. Insert a video iPod into this laptop-like device and you have something akin to a portable DVD player. This is a cool concept, but the screen's playback quality leaves something to be desired.
PodFreq. A weird-looking FM transmitter that works only with certain iPod models, but a steal at its new, lower price. I couldn't achieve decent sound quality with the nano version, though.
iBlastFM. A dock that holds a nano and has a long, flexible arm that fits into a car's accessory port (imperfectly, in my case, which caused playback interruptions). You're probably better off with Griffin's TuneFlex nano.
iTrip Auto. This FM transmitter and car charger is compatible with any relatively recent iPod, and works well. Thumb's up.
i-Station8. This iPod speaker system isn't obscenely expensive and sounds terrific. It's available at Best Buy.
TuneCenter. I liked this "home media center" dock, which lets you do photos and tunes along with videos on your TV set. If you plug into your home network via Ethernet, it will even tune in radio stations over the Internet.
Volta. Sonnet's video-iPod battery pack boosts video-playback time to 16 hours and looks way refined, but adds a lot of bulk.
Disko. Griffin's polycarbonate video-iPod case incorporates 70-style lighting effects. Cheesy, but in a good way.
Centerstage. This Griffin video-iPod case has a metallic flip-out attachment that turns this accessory into a stand for video watching on a tabletop or airliner tray. Nice.
