Lightning App Builder is a point-and-click tool that makes it easy to create custom pages for Salesforce1 and Lightning Experience.

SOGo (Scalable OpenGroupware.org) is an open source collaborative software (groupware) server with a focus on simplicity and scalability.

Memotoo sync all your contacts from Gmail, Facebook, phone, Thunderbird, Outlook, etc in a single address book.

Kolab is a free and open source groupware suite.

Baïkal is a Cal and CardDAV server, based on sabre/dav, that includes an administrative interface for easy management.