The idea is simple: Engage America picks heavily trafficked websites in key states (eg. the Orlando Sentinel, the Cleveland Plain Dealer) and enables its users to engage in fact-based debate in the online comment sections of the relevant media outlets in the relevant states. This allows people who live in states that are safe for either Obama or Romney to engage with voters outside their locality. According to Engage America, online comment sections are one of the best ways to influence persuadable voters.
I took the following video of their presentation; I apologize for the fact that the image is off by 90 degrees, but it gets the point across:
This is a FANTASTIC idea; I strongly encourage you to visit Engage America and learn more.