One of the new features of OS X Leopard is the 3D dock. While not the worst thing I've seen, it just seems out of place for the normally minimalistic Apple environment. What I do like is the look of the dock when moved to either to the left or right hand side of the screen. It becomes 2D with a dark transparent background and a single clean line surrounding it. Unfortunately having the dock on the sides never works for me. I usually have my IM open on one edge and desktop icons on the other side, not to mention the chaos caused by adding multiple monitors.

After a brief search I came across the free application 2DOrNot2d by Eternal Storms Software that can change the bottom dock from 3D to 2D. Once you launch the app you get a single button window that toggles between the two layouts. It could not be simpler, yet the effect (in my opinion) is dramatic.

Before:

After:

[Eternal Storms Software]