SquirrelMail

Powerful plugin that takes your WordPress.org powered site beyond the blog with social-network features like user profiles, activity streams, user groups, and more.

Powerful open source social networking engine.

Web-based open source GUI that controls and manages Asterisk.

Flat-forum bulletin board software solution that can be used to stay in touch with a group of people or can power your entire website.

Email forwarding service for creating aliases.

Easy to use but advanced IP PBX system, VoIP gateway and conference server.