The CDC's Center for Health Marketing has become both a thought and a practice leader in the use of social marketing and health communication (which they term "health marketing") to bring about healthy communities. They have especially taken the lead in using Web 2.0 and e-tool technologies to achieve public health goals! Their website is chock full of examples of applications and global initiatives; resources and tools; research and evaluation links; health marketing basics; and more--including a blog by Jay Bernhardt, Ph.D. center director, and my favorite, their e-Health Marketing Page!! (Don't miss the e-Health Data Briefs--wonderful one-to-two page PDFs with audience research about who is using 
which e-technology!)
The center's great work is summarized in a recently released report, "Health Marketing for a Healthier Nation and a Healthier World." It is available as a PDF from their web site.
