Microsoft Commerce Server 2009 code name “R2” August Community Technology Preview (CTP) is now available. This pre-release version of Commerce Server 2009 “R2” into a non-production environment to learn how Commerce Server 2009 “R2” provides an improved business management experience, enhanced cross-channel enablement with 3-tier development and deployment support, and a more streamlined deployment experience. Its recommended that you install this pre-release on a clean machine and consult the Installation Guide for manual steps required.

Download: Commerce Server 2009 code name "R2" ISO | Installation and Configuration Guide (doc)