One of the neat features of the iPhone, is the way its display switches automatically from portrait to landscape mode when you rotate it. Therefore, it seems obvious that any dock should let you do the same thing; but most are fixed in the vertical portrait mode.

This very cool dock made by Steven Combs not only lets him rotate his iPhone, it also has an appropriate high-tech look made entirely from gray, black, and white Lego parts.

While there are a couple of commercially available rotating docks, you could always just copy Steven's design and make your own.