The PBS Democracy Project site features some great interactives to visualize social studies concepts, particularly around Constitution Day.
The President for a Day activity allows students to assume the role of President and make decisions to plan his or her day. The activity lends itself well to using a graphic organizer to emphasize the text structure of sequence.
How Does Government Affect Me allows you to scroll around a town and view the interactions between government in our lives. This activity would result more in a list on a graphic organizer.
The website also allows you to register and create a sticker related to an issue. This was geared toward the 2008 election, but would still make a nice descriptive activity.