Here are some plugins that I have downloaded into wordpress:
Buddypress is easy to use and is there to make the wordpress site into a social networking site.
bbPress plug in creates a discussion forum.
BuddyPress Activity Plus
BuddyPress Activity Plus plug in uploads your images, videos and links with web.
Friends for bbPress
Friends for bbPress adds your friend button into your social network website.
iFlyChat is real time chat in your social network.