One thing you probably knew Firefox did, but might have never explored is applying a custom theme/skin. The latest release of the popular browser fully supports this functionality and even offers a theme repository on their own site.

There are tons of themes available and you can probably find one for just about anything you can imagine, so take a look. Vista users (or fans of the Vista Aero look) might want to check out the Aero Silver Fox theme which shares a similar look.