E-WRITE | Guide to Writing for Social Media

E-Write developed a writing guide for the U.S. Centers for Disease Control that's available free at this site. You'll need to provide your email address before downloading it -- but the guide looks like a useful tool.

E-Write writes:

While the examples [in the guide] will be most relevant to health communicators, the guidance about writing for social media is practical for any organization that wants to provide high quality social content for customers and readers.