Tomoye is the community and social platform for SharePoint

Tomoye has nine years of experience in making communities and social networking work for business users wanting to promote learning, cross enterprise collaboration as well as partner and customer collaboration. Read about the business results we help implementers deliver.
Over this period we have developed and deployed leading edge community, social networking and social media features and delivered in a way that you will ensure adoption by your users. The capabilities we have developed are modeled after those on the public internet so that your users will feel instantly comfortable.
For technical administrators, you will love our open source architecture with an open Web UI layer, full API, deployed directly on SharePoint - both the free and enterprise versions. This allows you the flexibility to do whatever you want.