The Microsoft HPC Pack 2008 R2 and its SDK have been updated to 'Beta 2'. There have been a lot of changes since the Beta 1 release last year, so come and check it out:
If you have never joined the HPC Pack 2008 R2 beta program you can do so here: http://connect.microsoft.com/HPC/InvitationUse.aspx?ProgramID=3069&InvitationID=3gen-FD4X-XGF7
Otherwise you can access the new downloads here: http://connect.microsoft.com/HPC