The Release Notes for Windows Vista Service Pack 1 just appeared on the Microsoft Downloads Site. 
And just after this Microsoft posted a Media Alert: Microsoft Releases Windows Vista Service Pack 1, Windows Server 2008 to Manufacturing.
Finally!
Vista Service Pack 1 will be available “to customers in March” and Windows Server 2008 will “be available […] on March 1”.
When will it be available on Microsoft Downloads or for MSDN/TechNet Subscribers?
Update: The Windows Vista Team Blog has detailed timings for Vista SP1
Update 2: Windows Server 2008 is available for MSDN and TechNet Subscribers
Let the fun begin…