RocketDock is pretty cool, but I guess I grew tired of the novelty quickly.
Another app in the same vein is True Launch Bar
http://www.truelaunchbar.com/Not quite as pretty/polished, but packed with options, and included tons of plugins to do just about anything you'd want to do in the taskbar or a sidebar. I've found it much more useful in the long run, but hey, tastes differ

It's not free, but it's cheap enough that it's not a big concern, plus they have a long trial period.