Mightybell - Build a community and a business on mobile
SaidIt.net - Saidit.net - say your truth.
MyTalk - Build a community around your product
Reddit - Reddit gives you the best of the internet in one place. Get a constantly updating feed of breaking news, fun stories, pics, memes, and videos just for you.
Hey.Cafe - Hey.Café is a social network built around communities called cafés.
Raddle - A web-based forum where users submit links, pictures, posts, etc.