BuddyPress.org

Try starting with a premium City Guide theme from Woo themes. http://www.woothemes.com/2010/03/cityguide/ and merge it with buddypress. That theme is already a big plugin itself combine it with bp for something pretty cool. Then there’s this business directory plugin that you could throw in there for the complete package – http://themestown.com/wp-business-directory-manager. Its been on my list of things to do to make a hybrid of those three. Look forward to seeing what you come up with. Salu2