Python 2.6.6 is the newest and last maintenance release for the Python 2.6 series.
Going forward, only security fixes will be made to Python 2.6 until its end-of-life in October 2013. There will be no new features or bugs fixed.
Version 2.6.6 fixes dozens of issues with the core, built-in modules, libraries and documentation.
For ongoing maintenance releases, upgrade to Python 2.7.