Biznik is for people who are passionate about what they do and want to be part of a community of like-minded folks interested in seeing each other succeed. The network also has location specific groups.

Ning offers an easy-to-use service that allows people to join and create online networks. You can find a wide range of niche communities to join and participate in. Each one allows you to create your own page and offers a very simple interface to connect with other members.

Meetup is the world's largest network of local groups. The website makes it easy for anyone to organize a local group or find one of the thousands already meeting up face-to-face. Definitely check out if you are interested in a local community that gets together to network, socialize and show-and-tell thier interests.