SocialEngine - Socialengine PHP: Elevating Your Online Community Experience.
Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
phpFox - phpFox is a powerful social network platform for niche communities
Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.
BuddyPress - WordPress social networking in a box.
Influitive - Influitive helps companies increase customer lifetime value and accelerate sales with the power of their own customer advocates. Inspire your customers to stay longer, share their experiences, and attract new business.