More fun with -moz-box-shadow (as with http://freestyler.ws/style/15420/userstyles-org-users-menu-all-in-a-row, Firefox 3.5 and above only, and also moves the "menu" from a column on the left to a row along the top under the header). Review the code--it's easy to substitute your preferred colors.

Note: The screenshot shows this style as it looks when used with my http://freestyler.ws/style/15318/userstyles-org-my-mod-of-british-blue style (which is to say, it's primarily a modifier style for that one, for now). Obviously, it could look different when combined with other styles.

Updates...
09Aug2009: adjusted padding for default site styling (should look OK now even if you're not using my aforementioned style)