WordPress is an open source blog tool and publishing platform powered by PHP & MySQL.
This MeetUp group gives presentations and holds discussions about WordPress technical aspects and business applications.
WP can be used under wordpress.com as a simple blog. Or, download the code from wordpress.org and customize your own Content Management System. It has many dynamic features, including a plug-in architecture and a template system.
Our group's WordPress blog is SaratogaMeetup at saratogameetup.com where everyone is invited to contribute.