You could use my flex accordion to get this effect. Right now it generates a navigation, but you could make it display pages and/or posts with a little php knowledge.
http://wordpress.org/extend/plugins/flexible-navigation
This is a totally awesome plugin. I used it to create a registration system for an internal company site. Also for feedback forms, I use Cforms II in conjunction. By having all the extra meta added on first registering a user, it is possible to do many neat things once they log in, like pre-fill Cforms forms. present profile information on post etc. Very nice.
