FUDforum (Fast Uncompromising Discussion Forum) is a free and open source web discussion forum.
FUDforum combines an extensive feature set while maintaining the ability to generate forum web pages extremely fast. The forum includes i18n and templating support allowing for a complete customization of its output as well as a very capable group based permission system.
FUDforum can also act as a Mailing List Manager, USENET newsreader and even an XML Feed Aggregator. This will allow you to build an instant community and consolidate all your messages into a single system.