Free and open source webmail software
FUDforum is a super fast and scalable discussion forum. It is highly customizable and supports unlimited members, forums, posts, topics, polls & attachments. It can import XML Feeds and sync with USENET groups and Mailing Lists (bi-directional).
A web-based project management tool for workgroups. Encourage groups and individuals to work collaboratively. This tool aims to be functional and elegant without being complicated or graphically intensive.
Simple Picture Gallery Manager is a PHP script which generates online photo albums and features very simple setup and update procedures. Highly configurable though, it includes several options for smooth integration.