Social Studies electronic resource

We are creating a Wiki for elementary social studies resources. We want to include maps, readings, primary sources, games, "electronic field trips", etc. Has anyone done this and do you have any tips for organization, resources, how you included web 2.0 tools in specific areas that worked especially well? We are beginning with the fourth grade, i.e., immigration and regions of the U.S. I would like to include some activities like e-pals with other regions of the U.S., collecting oral histories from our community members and creating an online archive. I'd like to hear some of your ideas...