SMF

Words like elegant, effective, powerful and free are used to describe the SMF forum sofware script by Simple Machines. SMF is a next-generation community software package with good features and low resource usage.

Some of the SMF features include:

• Comprehensive themes that allow forum administrators to control the default theme and users to select themes
• A fast and efficient MySQL database
• Secure, uncorruptable file attachments.
• Automatic mod installation allows admins to download and install upgrades and modifications quickly and easily.

More info about SMF can be found at http://www.simplemachines.org.