Overview of Windows Vista Service Pack 1 Beta
According to a press release it will released in Q1 2008.
From the Windows Vista Team blog
Microsoft's efforts to provide the best Windows experience ever in Windows Vista did not end with its launch. This white paper describes the ways Microsoft strives to continuously improve Windows Vista. It then introduces Windows Vista Service Pack 1 (SP1) and describes how the service pack will fit into the ongoing improvement process.
You can download the XPS version of the Windows Vista SP1 Beta Whitepaper here from our Public Windows Live SkyDrive folder:
http://cid-bbb1ef94681f0a70.skydrive.live.com/self.aspx/The%20Windows%20Vista%20Team%20Blog/Windows%20Vista%20Service%20Pack%201%20Whitepaper%20August%202007%20FINAL.xps