Choqok is a Free, Open Source micro-blogging client for K Desktop Environment.

Friendica (Friendika or Mistpark) is open source software for a distributed social network. The focus is on effective privacy settings and easy installation …

Jostle is a people engagement platform mainly focused on employee engagement.

Minds is an open source social networking service.

Simplify360's Social CRM helps understand what your customers are talking about you and engage with them as and where they prefer.

Yammer is a freemium enterprise social networking service used for private communication within organizations.

Ello is a community to discover, discuss, publish, share and promote the things you are passionate about.

GNU social is a continuation of the StatusNet project. It is social communication software for both public and private communications.

Known is a publishing platform that allows its users to share their stories online.

Plurk is a free social networking and micro-blogging service.

Twitter is a social media platform for broadcasting short messages to the world and followers.