The Bose SoundDock.  Really.  It is way cool.  It is way expensive too but given the simplicity, elegance, and sound quality it is well worth it.  Too many iPod docking units have subwoofers, separate speakers, lots of switches, look clunky, etc.

When I told my wife I was going to put a stereo in our living room that she had meticulously decorated she gave me a very skeptical look.  Then I brought the SoundDock home and she liked it pretty much from the get go - "you mean I just plug my iPod in and that's it?"  Yep.  And it charges the iPod as well so I/she can just grab it and go.  Since we got it we've had a lot of guests and pretty much everyone is amazed at the sound produced by that little gizmo.  I'm sure we've inspired a few iPod and Bose purchases.  The downside is that the SoundDock isn't very versatile - it just works with the iPod and that's it.