Plastic Pulse is a free and plastic themed, smooth looking theme for all Leopard users that have a sweet tooth for interface customization and want to change their default OS X theme to something different.
Copy Sartfile and Artfile to the /System/Library/PrivateFrameworks/CoreUI.framework/Resources/ folder.
Copy Extras2 to /System/Library/Frameworks/Carbon.framework/Versions/A/Frameworks/HIToolbox.framework/Versions/A/Resources.
Restart and enjoy.
Plastic Pulse is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.