Not to be confused with Windows Server 2008 R2, Windows Vista and Server 2008 service pack 2 (SP2) was released to manufacturing yesterday, the same day the the blocker tool for Windows Vista SP1 was removed (Windows Server 2008 shipped with SP1 included).
Full details of the service pack may be found in Microsoft knowledge base article 948465 and there’s also a notable changes page on the Windows Client TechCenter. In addition, Microsoft knowledge base article 969707 gives details of some of the applications that might have problems after installing the service pack.
[Update 30 April 2009:
There’s no download link yet – the official line is that public availability is expected later this quarter. TechNet and MSDN subscribers can now download SP2 and I’d expect to see a public download link at the Windows Client TechCenter soon.]