Microsoft has published Service Pack 2 for Windows Vista and Windows Server 2008, you can grab it over here:
32-bit and 64-bit. A list of notable changes in SP2 can be found at TechNet.
Service Pack 2 for Windows Server 2008 and Windows Vista (SP2) is an update to Windows Vista and Windows Server 2008 that supports new kinds of hardware and emerging hardware standards, and includes all updates delivered since SP1. SP2 simplifies administration by enabling IT administrators to deploy and support a single service pack for clients and servers. Please see the Windows Server SP2/Windows Vista SP2 page on TechNet/MSDN for additional details and documentation.
SP2 is an update to Windows Server 2008 and Windows Vista that incorporates improvements discovered through automated feedback, as well as updates that have been delivered since SP1. By providing these fixes integrated into a single service pack for both client and server, Microsoft provides a single high-quality update that minimizes deployment and testing complexity for customers.