Google SketchUp is a great tool to create maps.
Import Google Earth images into SketchUp to create topo maps and models.
Video tutorial: "How to Create a Topo Map with Sketchup" from Designer Hacks
Below is a list of sites with a limited number of digitized Sanborn Fire Insurance Maps made available through various state and academic institutions. These are older maps now in the public domain. To see a large, beautiful, physical 2-volume set for Springfield from 1956, head down to the Library Center on So. Campbell to the local history rare book room. It's worth the trip.