We just announced the CPP (Customer Preview Program) for Windows Vista SP2 and Windows Server 2008 SP2. This Beta is now available if you have a TechNet Subscription and it will soon be available for everyone to download and test. Since we have the same code base for both the clients and server they share the Service Pack so you just have to deploy one single update.
The Service Pack Beta includes previously released security updates, support for new types of hardware and fixes that we discovered through the error reporting form customers. You can find more details on what exactly is included together with deployment guidelines, bug reporting and FAQ on TechNet