Windows Vista and Windows Server 2008 Service Pack 2 Release Candidate has been released today for Technet and MSDN subscribers.  Microsoft plans to release the RC to the public in the "very near future" according to the Windows Team Blog.

Starting today, the RC of SP2 for Windows Vista and Windows Server 2008 will be available to TechNet and MSDN subscribers to test prior to final release. In the very near future, we will be making the RC broadly available for anyone to download and test. You can expect another blog post from me when that happens.

Read more on the Windows Team Blog