We just shipped Rights Management Services (RMS) SP1. It is Microsoft's latest release in the Enterprise Rights Management (ERM) space. It comes with a host of new features to improve deployment, support for high security environments like air-gap networks and conforms to FIPS standards. More importantly, SP1 provides support for a host of server-side solutions to be RMS-enabled. Check out the ten great things about SP1 here.
 
You can download RMS SP1 for windows server 2003 (this is the RMS server) here.  The client software is available here.
 
*Update* Eweek and BetaNews have a great coverage on RMS SP1 here and here respectively.