Social Web Directory :: Social Network Directory :: Ning Tips and Ning Support
http://labsecrets.com/ recenty started a new sollution for creating your very own Social network, build upon the Wordpress and Buddypress engine.
Buddypress is known as the most robust system to create a very cool social network, build upon Wordpress.
Eventhough i find their plans quite expensive, the idea is great and especially for professionals it seems to be a very interesting sollution!
You can read their plans here: http://labsecrets.com/plans/