It depends if you actually want good quality, or very good quality, or just crap...(im guessing not the latter of the options).
Two docks that stand out above basically everything else are these two, the Bower & Wilkins Zeppelin and the NEW Bose Sound dock(the one with the rotatey thing on it):
The B&W -
The Bose Sound dock (rotate thingy allows you to hide the sound dock when not in use):
The Bose Sound dock (rotate platform shown with a docked iPod in it):
With all these, the only thing that you need to connect your computer to the speakers is a 3.5mm-to-3.5mm jack, one that you can easily find of relativly good quality for about £15. The cable basically has two end that look exactly the same, and each end looks like the end of a standard set of headphones, as mentioned in an earlier post