The documentation for volume activation 2.0 has been updated today for Server 2008. You can find it here:
Running KMS on Server 2008 is functionally very similar to running it on Vista RTM. You leverage slmgr.vbs to bring the service online and then clients find the server based on the DNS srv record. BTW, Server 2008 KMS can be run within a virtual environment.
There are online videos to understand volume activation and how to setup a KMS host if this is all new to you. See the links below.
Setting up KMS - http://go.microsoft.com/fwlink/?LinkId=104718 VA overview - http://go.microsoft.com/fwlink/?LinkId=104707
If you want to know which volume license keys to use when activating new machines running Server 2008, see page 19 in the Planning Guide and the FAQ. You only need to put one key in your KMS, and it will handle requests from both Vista and Server 2008. There are separate keys, and unique keys based on which version of server you need to activate. Before you get excited - this is much easier to understand than it might first seem. Simply decide the "top" version of Server 2008 you might install and then use that MKS key to activate the service on a 2008 server. All versions in groups below that version will also activate off that key. The groups are simple.
The groups are named "C, B, A, and Client" respectively. So if you want to activate Server Enterprise, Standard, and client machines, just use your B key to bring the KMS online and the work is done.
The other major change from KMS 1.0 is that in order to activate servers you only need 5 machines online, vs. 25 to activate clients. The client activation still only comes online after you have 25 machines activating, but servers will begin activating after 5. The 5 do not have to be all servers. I mentioned above that KMS 2008 can be run in a virtual environment, which is a change from KMS 1.0. The client requirements have not changed, they can be physical or virtual but only the physical count towards your initial 5 or 25.
Just in case you missed the link above, the table listing which versions of Windows are in each tier is up to date on this page - http://www.microsoft.com/licensing/resources/vol/ActivationFAQ/default.mspx See - Are there any changes with Windows Server 2008 keys?
Last, there is also an MAK for Server 2008 just as there was for Vista, and it works much the same way. The key tiers for MAK are relative to the same groupings as KMS, but differently from KMS they do not support the groups under them. So you will have an MAK for Vista, and an MAK for Server Web, Server Std/Ent, and Server DataCenter/Itanium respectively.
Just wanted to add a note on adopting this for Server 2003. Server 2003 installations will continue using the VLK as they have in the past, but will get an update for being a KMS host that can activate Server 2008 and Vista. It will then have support for the tiered keys I mention above. Look for this "KMS 1.1" update in the coming weeks. It will also support running in a virtual environment.