Longhorn Transformation Pack
If you have Windows XP or Windows 2003 then you have got to download and apply the Longhorn Transformation Pack, the Plex theme include is way cool and makes your taskbar smaller giving you extra real-estate space on your screen. Some of my coworkers are green with envy over my desktop. (Remember to backup your data, the Transformation Pack has been reported to have screwed up a number of machines).