Library of Congress has made available for download over 2000 Civil War era battle maps and various other maps. The server is being hit pretty hard right now with downloads, but you might try it late at night or in a few days. I was bale to get through, but it ran really slow.
http://memory.loc.gov/ammem/collections/civil_war_maps
The Library of Virginia has also made several hundred maps available. Don't have a link for them.
Regards,
RoB Stone