BuddyPress.org

try this one. I had written about it in forum, so you can find it by searching the forum. Or check my post here

http://www.thinkinginwordpress.com/2009/11/tweaking-the-registration-link-at-wpmu-login-page-to-point-to-buddypress-registration-page/

That should do the trick.

Thanks

Brajesh