ownCloud is a free and opensource file sync and share app which is self hosted.

Zentyal is an open source email and groupware solution based on Ubuntu Linux.

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

Kopano is an open-source groupware application suite originally based on Zarafa.

Zarafa is an open-source groupware application.

eXo Platform is an open source, standard-based, Enterprise Social Collaboration Platform.

Kolab is a free and open source groupware suite.

Zimbra offers an open source email platform for the enterprise.

NethServer is an operating system for Linux enthusiasts, designed for small offices and medium enterprises.

OX Open-Xchange is a web-based communication, collaboration and office productivity software.