After releasing various developer versions of Mac OS X Mountain Lion, now quite a stable Mac OS X Mountain Lion Developer Preview 4 is out there for testing by registered Apple developers that includes fixes for issues and new improvements.
If you are an Apple enrolled developer then head to Developer Center to download Mac OS X Mountain Lion Developer Preview 4.
See also:
WWDC 2012 KeyNote Video
iOS 6 Features
Download iOS 6 Beta
Download iTunes 10.6.3