Commerce Server 2007 code name "Mojave" November 2008 Community Technology Preview (CTP) is available for Download from the Microsoft Connect Site.

Microsoft Commerce Server 2007 Code Name “Mojave”  November 2008 CTP release is now available for download from Microsoft’s Connect site.  
It features notable updates to the new commerce foundation API, as well as the complete gallery of 29 new Web Parts for use in SharePoint, and an early version of the un-skinned Default Site containing most of the Web parts. Also included is a getting started API sample and a great set of documentation.  See the documentation and readme file in the release for a full listing of the changes.