Beehive Forum is a PHP/MySQL discussion forum, The main ones are listed below:

• Frame-based layout, for easy navigation.
• Reply-to-user posting and e-mail notification.
• Powerful HTML posting, without security risks.
• Extendable user profiles.
• Flexible relationships system.
• Private Messaging system.
• Multiple style options, including dyslexia support.
• Advanced word-filtering facility.
• Comprehensive user permissions.
• Full, easy to use admin tools.

更多：http://beehiveforum.sourceforge.net/about/