That's right, if you are building an application that will run on Windows Server 2008 you should begin looking at certification now!  There is a ton of information on www.invoateonwindowsserver.com, so much so that we've turned the certification test into an "open book" exam.  

Microsoft developed the Certified for Windows Server program to help you build greater quality into your applications and to distinguish them in the marketplace.

The most visible benefit of the program is the "Certified for Windows Server" logo. When displayed on your product packaging and promotional materials, it helps customers instantly recognize that your applications have met higher standards of reliability, security,
and compatibility.

I've also posted a great little intro video here.