SOGo - SOGo is groupware server with a focus on scalability and open standards.
MINDBODY - Find and book fitness and beauty classes near you.
Baïkal - Cal and CardDAV server
Kajabi - Kajabi is the only Knowledge Commerce platform today with everything you need to market, sell, and deliver your knowledge online.
Xandikos - Lightweight CalDAV/CardDAV server on top of Git.
Tendenci - Tendenci - The Open Source AMS is a cloud-based all-in-one management SaaS solution for Non-profits and Associations.