E-Democracy.Org provides practical advice on the use of technology in civic engagement. We have over 15 years direct experience on how to engage people in a pragmatic practical manner online including advancing "social media" opportunities (without wasting precious resources on inflated expectations).
We are technology "user" (not developer) but share our intellectual capitol with the GPL open source GroupServer.Org tool. It combines highly accessible e-mail list with web forums and increasingly social media/web 2.0 elements. This is the lowest cost tool for sustained civic interaction online that we are aware of online that you can use with your own domain. There are dozens of free tools that simply don't work well with small geographic communities unless you have well paid staff or a dedicated volunteer editor producing extensive content.