PoliticalModeling.com: District Explorer

Truth to be told, I don't know about this one. It allows you to plot various attributes (historical election results, demographics, land area, economic numbers, etc.) for all 435 Congressional Districts, and also to simultaneously winnow down the districts by creating selection criteria for inclusion. If you want to look for broad voting trends or to look for districts with high numbers of African Americans, for instance, this would allow you to do so.

I've written a more general description on my blog. If you have thoughts or questions feel free to contact me directly at drdavegoldberg@gmail.com.