SpotPress is a cosmetic redesign for the WordPress admin pages that resembles the Spotlight search window in Mac OS X 10.4 Tiger. It uses WP’s excellent plugin architecture to simply insert the new stylesheet without any code modification or hassle.
SpotPress is definitely my favorite WordPress Admin/User Interface so far. At v0.8b, SpotPress is still incomplete, but it is 99% functional and easy to install and uninstall if need be. If changing your WordPress Admin/User Interface is of interested to you, you can find more Admin Themes in the Codex list of WordPress Admin Themes.