I had to recently apply some funky arrowheads, colors, and styles to a scrollbar attached to an overflow'd DIV element, and discovered the Holy Grail of jQuery scrollbar plugins - jScrollPane.  If you aren't using it, you should be.

This thing rocks.  The author has provided almost every conceivable example, downloadable starter stylesheets, and good documentation (more that you usually get with a plugin).  Best of all, it requires no modification to your markup to prepare it for the scrollbar.  You simply execute a jQuery selector and call the jScrollPane entrypoint on the result set, and the plugin does the rest.

Check it out and add it to your toolbox!