ownCloud - ownCloud is an open source project enabling businesses to host their own cloud storage while maintaining regulatory and compliance needs.
Baïkal - Cal and CardDAV server
DSpace - DSpace open source software enables open sharing of content that spans organizations, continents...
Radicale - The Radicale Project is a complete CalDAV (calendar) and CardDAV (contact) server solution.
SOGo - SOGo is groupware server with a focus on scalability and open standards.
BitKeeper - BitKeeper is an open source distributed version control tool.