While the OS-specific keys are sometimes called super, they are not "super" in emacs terminology. Also, if you skim M-x describe-bindings you will find quite a few bindings beginning with s-.
EDIT: If you really want access to a less crowded namespace, using (global-set-key "\C-z" nil) to free up the c-z prefix and binding Hyper are popular.
If you are feeling a little confined, key chord[1] will allow you to get creative with your bindings.
EDIT: If you really want access to a less crowded namespace, using (global-set-key "\C-z" nil) to free up the c-z prefix and binding Hyper are popular.
If you are feeling a little confined, key chord[1] will allow you to get creative with your bindings.
[1] http://www.emacswiki.org/KeyChord