Are there any books/platforms for social media campaign planning and implementation that define a completely agile approach to engaging audiences on platforms such as Facebook, Linkedin, Twitter, etc?
UPDATE: Posted a bounty on the question since the current answer is really not about agile approaches to social media campaign planning and implementation.
UPDATE 2: The question is asking for an agile social media approach, or a social media platform that has agile social media approach baked-in.
If the question was about an agile approach to software development, SCRUM would be the most likely answer of an "agile approach", since it's my understanding that roughly 70% percent of agile software developers say they practice some form of SCRUM. Pivotal Tracker might be one of many "agile software planning" platforms suggested; as a generalization Pivotal Tracker might be called a software project management platform.
On the flip-side, suggesting just a "social media platform" might be the equivalent of suggesting a "project management platform"; meaning the suggestion lack a suggestion of both an "agile social media platform" and "agile social media approach", and the problem is that if you haven't suggested an agile social media approach to try on this social media platform, then you haven't provided an answer to the question.