Just had to share this little how to, as I've tried lots of these rename hacks for the WP admin and none of them have really worked; this one has for me though.
Looking at the code, I think it could probably work on any CMS... but I've yet to try it on anything other than WordPress.
Thought I'd try and put something back after all the help I've read here:
http://www.voodish.co.uk/articles/rename-wordpress-admin-directory/