From "Emacs for vi programmers", http://grok2.tripod.com/:
(defun match-paren (arg) "Go to the matching paren if on a paren; otherwise insert %." (interactive "p") (cond ((looking-at "\\s\(") (forward-list 1) (backward-char 1)) ((looking-at "\\s\)") (forward-char 1) (backward-list 1)) (t (self-insert-command (or arg 1))))) (global-set-key "\C-x%" 'match-paren)