There are quite some gadgets around the iPod. This page gives a small selection of links to useful, or just funny gadgets.
The Apple US store gives a useful overview of iPod articles.
Griffin technologies carries all kind of handy stuff for the iPod. Escpecially the iTrip is a usefull gadget, though forbidden (Dutch) in a lot of countries (silly!). For usefull radio station, look at ipodetc.