Thanks ooo who has informed me that a new beta has been added to his contact info details, this is typically where all new beta programs appear before becoming icons on the main page of BetaPlace.com (for logged in users). It appears that Windows Server 2003 Service Pack 1 will start soon as shown in this image. Windows Server 2003 was released worldwide in April 2003 and the first service pack usually takes a year after that, a summer start for an early 2004 SP1 release sounds about right.
Additionally BetaPlace has put up a new survey for the Windows Update v4 beta. it asks "For what operating system(s) are you most interested in receiving updates?" and the list is quite extensive, even lists Windows versions that aren't supported anymore (Windows 95 and NT4) and all versions after that. Windows XP Media Edition, Tablet Edition and Pre-install Edition have not been included in the listing for some reason.
We'll keep you updated as we learn more about these betas :)