
Version 12.2 ("Neil Armstrong") of the Joomla Platform was tagged and released on 21 September 2012. It is the second release of the 12.x series. Joomla Platform 12.2 was also included in the Joomla CMS 3.0 release. In addition to numerous bug fixes, it also brings new features, the main ones:
With the addition of Composer and PHARchive support in this release, the Joomla Platform extends its available distribution channels and formats.
The full list of commits is available here https://github.com/joomla/joomla-platform/commits/12.2 and the api doc here https://api.joomla.org
The Joomla Project is pleased to announce the availability of Joomla 3.0 Alpha 2 for download.
The main goal for this release is to allow advance testing of the new admin and site templates based on the Bootstrap framework. This release also 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.
For known issues with the 3.0 alpha-2 release, see the version 3.0 Alpha-2 FAQ in the documentation site.
This alpha version of Joomla 3.0 is not suitable for production sites. It is for testing only.
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.
For known issues with the 3.0 alpha-1 release, see the version 3.0 Alpha-1 FAQ in the documentation site.
This alpha version of Joomla 3.0 is not suitable for production sites. It is for testing only.

Version 12.1 ("Louis Landry") of the Joomla Platform was tagged and released on 9 May 2012. It is the first release of the 12.x series. In addition to numerous bug fixes, it also brings new features, the main ones:
The full list of commits is available here github.com/joomla/joomla-platform/commits/12.1 and the api doc here api.joomla.org
(Cross posting of Joomla Community Blog)
The next Joomla Roadmap Meeting is being held as part of the J and Beyond conference that is taking place May 18-20 in Bad Nauheim, Germany. Ideally, we'd like to come out of the meeting with some tangible accomplishments, but we recognize that may not be possible given the time constraints. More important is to bring people together to bounce ideas around and to form groups that will work to bring particular features into Joomla.
Read more: Joomla Roadmap Meeting: Production Working Groups & Lightning Talks