Here is a comprehensive review of positive and negative externalities. It includes the difference between marginal social cost and marginal private cost as well as the difference between marginal social benefit and marginal private benefit. Again there is no review activity for this one, but I'll start making more of those after I make a few more Microeconomics content review articles.
All of the Games and activities are in adobe flash format so they will not work on Android or IOS. There is an Android Economics Review App available in the google play store and I hope to make an IOS game sometime next year.