http://lesscss.org/
Magical stuff. Less is Leaner css. Less extends css by adding: variables, mixins, operations and nested rules.
http://wordpress.org/extend/plugins/wp-css/
The WP CSS plugin combines multiple CSS files used by WordPress into one single, gzipped file for faster download, fewer connections.
http://www.i-marco.nl/weblog/archive/2007/05/27/on_a_quest_for_ultimate_websit
May 2007 - A guide to optimising WordPress focusing on browser led optimisations such as fewer http requests, spreading images over hostnames, and so on.