The OpenGL Samples Pack 4.2.0.0 is the first version covering OpenGL 4.2 features with 10 samples.
Most of all the extensions introduced at Siggraph 2011 are covered by these samples.
The OpenGL Samples Pack 4.2.0.0 is available on Windows for Visual C++ 2008 - 2010 using CMake. Linux supports will follow soon.
UPDATED 1 - 10/08/2011: The OpenGL Samples Pack 4.2.0.1 is a quick fix release. Thanks to Piers Daniell for his help!
UPDATED 2 - 11/08/2011: The OpenGL Samples Pack 4.2.0.2 is an update to take into account AMD OpenGL 4.2 beta drivers which doesn't expose an OpenGL 4.2 context but extensions. AMD OpenGL 4.2 beta drivers fix a lot of issues previously reported.