There's a large database of user styles for many websites here: http://userstyles.org/ http://userstyles.org/ There's also http://userscripts.org/ http://users

There's a large database of user styles for many websites here: http://userstyles.org/ http://userstyles.org/ There's also http://userscripts.org/ http://userscripts.org/ which is the same but for JavaScript instead of CSS.