I'm a big believer in sharing what other agencies are doing, and happily, there are several sources for federal communicators who want to make the case for social media. Try these resources and links:
GovLoop.com, itself a social network for federal workers and anyone interested in the federal space, has lots of federal social media communicators blogging, Twittering and posting about their social media efforts and source documents. Dive in here!
The Federal Web Managers Council has posted its workplans and documents here, a rich trove that includes this paper on real and perceived barriers and solutions for social media use and examples of federal agencies using online tools.