Cool postbits are just require a good idea and a bit of work.
Synthesis owns:
http://www.zelaron.com/forums/index.php?styleid=1
One thing I noticed is that on some of the forums listed, the postbit sometimes got messed up because tables didn't size as expected the first time I loaded a page. Sure, refreshing made it go away, but you can write the HTML/CSS in such a way that tables not sized as expected have no/minimal effect on how it looks, depending on where exactly the problem occurrs. Of course, you could just call me a crazy perfectionist.