Joomla!

Home of Joomla!

OpenSourceMatters

Home of OSM

php.net

The language that Joomla! is developed in

Joomla! - Forums

Joomla! Forums

MySQL

The database that Joomla! uses

Ohloh Tracking of Joomla!

Objective reports from Ohloh about Joomla's development activity. Joomla! has some star developers with serious kudos.