Grou.ps is another platform that you should probably look into if you’re interested in building anything like a Social Network.
It’s got a very large range of features that will pretty much satisfy anyone:
As you can see, Forums, Wikis, Blogs, Calendars, Video, Files, Photos, Links/Bookmarks, Maps, Chat, and more!
One of the nice things is that you could even sign up for a free hosted-account and you won’t be spammed by any random advertisements. In fact, you can also mask a domain so that it looks like your own service!
Pretty amazing considering it’s all free!
Support on this platform, though, is pretty limited, so I would probably proceed with a little caution; you need to know what you’re doing and have a good handle on how to install, update, edit, etc.
Otherwise, knock yourself out.