Ning

Ning is a platform for creating your own social network. This web service puts new social networks in the hands of anyone with a good idea. With Ning, your social network can be anything and for anyone. You start by naming your network and choosing a combination of features (photos, videos, forums, events, etc.) from an ever-growing list of options. You can then customize how your network looks and launch! People who join your network will automatically have a customizable profile page and will be able to message and friend each other.

HiperLink: http://www.ning.com/