Lisa, Your post reminded me of a woman I ran into back in July. She's an author and expert on the subject of measuring public relationships. I enjoyed her book and our conversations. Read my post on the subject and scroll through it for links to her Web sites, book and presentations.
Her measurement techniques might be useful for your project. They helped me to get my head around measuring effectiveness in this space.
Great article in the Harvard Business Review (if you have access) this past month. Check it out if you can, it provides some good guidance. That guidance is also available here on GovLoop though. :)