The Joomla Project is pleased to announce the availability of Joomla 3.0 Alpha 1 for download.
There is one goal for this release: to allow advance testing of custom extensions so that extension developers can report any problems well before the final release. This release includes most of the platform changes that will be included with version 3.0.0. Some of these changes will require small changes to extensions. For a complete list of known backward compatibility issues for version 3.0 see Potential backward compatibility issues in Joomla 3.0 and Joomla Platform 12.1 in the documentation site.