At this time, we don't have any API access to post anything to 3rd party sites, such as Facebook or Twitter, for any of our products. Will pass that on to our developer teams as we are starting to work on exposing Social Campaigns features through our API.
What content would you be looking to post to Facebook? Anything you can provide so we can understand what you'd be looking to do can help us to make sure we work on the correct things.
Dave Berard Senior Product Manager, Constant Contact