UPDATE!!: Microsoft have now (27/04/2008) released the final redistributable CAB files. The below are the final English language CAB files you need for a BizTalk Server 2009 installation on Windows Server 2008:
The installation guides have links to the redistributable pre-requisites for other languages and operating systems.
The pre-requisites CAB files available at the moment for BizTalk 2009 on Windows Server 2008 are:
These CAB files have version 8.0 of ADOMD.NET in them. If you run into a problem with the RTM version of BizTalk 09 asking for version 10 of ADOMD.NET, you can download it from here: