Someone told me it is hard to notice if there are unread private messages. So I've written an extension to display an announcement, when a new private message arrives. That's how it looks:
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. blah blah blah
Download the source code at Gitorious.