Admin plug-ins

http://rudd-o.com/projects/wp-admin-themer/

http://codex.wordpress.org/Creating_Admin_Themes

http://wordpress.org/extend/plugins/adminimize/

http://wordpress.org/extend/plugins/easy-admin-color-schemes/

WordPress optimizing

CSS zipping and concatenating

http://wordpress.org/extend/plugins/wp-css/

Cache optimization:

http://wordpress.org/extend/plugins/wp-super-cache/

Database cleanup:

http://yoast.com/wordpress/optimize-db/