XDock

xdock is a software that emulates the Window Maker docks, with the following differences:
-runs in any window manager
-easy to program - programming the Window Maker docks was a hard job.

But xdock provides a API that makes programming much easier
-client/server - it works in a client/server way, where a server sits in the right side of the screen, and the docks are clients that connect to that server