Ning competes with large social sites like MySpace and Facebook by appealing to people who want to create their own social networks around specific interests with their own visual design, choice of features and member data. The unique feature of Ning is that anyone can create their own social network for a particular topic or need, catering to specific membership bases.
If you haven't taken the time to try out the new Ning today, Robert Scoble has filmed an excellent demo of the product (basically the same demo I saw yesterday) from CEO Gina Bianchini. There's a lot of coverage from other bloggers as well.
Groupsite ties together social networking and collaboration in an effort to make group communications easier and more efficient. It's a hosted solution with Pro plans and a free tier for social networks. With the free account, you can add individual premium features at $9/month each.
Groupsite has all of the features you would expect to find, including forums, calendars, blogs, file sharing, and profiles. Some have said that Groupsite is to Ning what Facebook is to Myspace. Check out our coverage here and go take it for a spin yourself.
SocialGo, founded in 2007, is more of a direct competitor to Ning as far as their goals. They allow "anyone to create a professional-grade social network for their group, business or interest." They are focused on expanding premium services, but do offer a free (forever) account to get your feet wet. If you don't really feel like setting up your network on your own, you can pay $149 and have a SocialGo Concierge do it for you.