I've recently spent a fair bit of time working on ConfigMgr R2 residing upon Windows Server 2008. There are a few issues in there that you'll need to become aware of, but it's not that difficult to get underway.

I was going to write up a good article on this one, but it seems I was literally only a few days ahead of some of the other posters out there, for example the Deployment Guys have a good posting on the subject.

Keep an eye on this procedure, don't follow these instructions to the letter, it's not a work sheet\tick list. You DON'T need to install the Domain Controller role on the Windows Server 2008 target server (the guy does state this is only a prereq for his lab!!!!)

http://blogs.technet.com/deploymentguys/archive/2008/08/07/how-to-setup-configmgr-2007-on-windows-server-2008.aspx

Anyways I thought I'd link up to that posting rather than put up my own (I know, such a lazy cheater I am!!!!)

All I'd add is to be mindful of being in Native mode, and requesting the certificates from a Windows 2003 Root CA (or subordinate) from Windows 2008.  There is a two-step shuffle work-around required, firstly a patch to modify the Web enrolment website files on the CA itself to support Vista\Server 2008, and then once you've retrieved the certificate the steps for moving the certificate+keys from the User store to the Computer store.

Firstly, the Server 2008 to Server 2003 CA issue is discussed here (Along with a side-issue on V3 PKI certificates not being supported on ConfigMgr 2007, always handy to know this stuff even if it's not applicable now)

http://blogs.technet.com/wemd_ua_-_sms_writing_team/archive/2008/06/30/having-problems-deploying-the-certificates-for-native-mode-with-a-windows-server-2008-ca.aspx

And the second step is required because the web enrolment ActiveX component cannot reach the Computer Store (Server 2008, change in security architechure for Iexplore) and thus the certificate+key is stored in the User's certificate store instead. No good for ConfigMGr, so the steps to move the certificates are covered off here, but keep in mind the certificate template MUST have "export keys" ticked before you issue the certificate for this to work:

http://support.microsoft.com/kb/939616

Rushed I am, new task master I have. But I will try to squeeze more time out to review this posting, see what i've missed, answer any comments et al.

Enjoy,