Download the April Update for the SDK here: http://www.microsoft.com/downloads/en/details.aspx?FamilyID=39856a03-1490-4283-908f-c8bf0bfad8a5

More detals can be found here on the Windows Azure Blog:

http://blogs.msdn.com/b/windowsazureappfabric/archive/2011/04/10/windows-azure-appfabric-caching-availability-announced.aspx