GigaTrust's (a Microsoft partner) Enterprise Trust solution has a nice feature for doing that:

Automated, persistent content protection is a necessary element of complete enterprise security architecture that seamlessly complements existing perimeter security solutions with content protection. GigaTrust Enterprise Plus provides the tools to automate the protection of your sensitive documents and intellectual property, and allows you to share those documents with colleagues as well as your business and supply chain partners regardless of where they are.

Jason Tyler, who does product support for AD RMS, also has some nice things to say about Gigatrust's products.