BuddyPress.org

@pjnu – I would use WPMU 2.9.2. You could already start developing and testing in WPMU 2.9.2./BP 1.2.4.1 where there are many versions-compatible BP plugins to play with. Furthermore, upgrading from WPMU to WP 3.0 is so much easier than setting up WP 3.0 and making it multisite (so many steps). Also, WP 3.0 rc2 with BP 1.2.4.1 is still quirky and many BP plugins do not work with the new set up as Pages will be used in rendering BP components. Just my 2cents to avoid frustration.