http://tnmap.tn.gov/civilwar_test/. It shows hundreds of places where Civil War battles and engagements occurred, which you can view with aerial photography, street maps, land use and property parcel maps (use the vertical arrow cursor at left to zoom in and out). You can find complete histories of all the units that served in the war from TN, searchable by county. We have linked many images and documents from the TSLA collections to sites, and overlaid old Civil War maps onto the current landscape.
Play with it, click the buttons and tabs, and show it to your kids. They might like it!
UPDATE 6/16/2011: In a press release on Wednesday the Tennessee Department of State formally announced this project to the public.