Good stuff but it can't top the Delaware Geological Survey's georeferenced maps from the 1868 state atlas: "Delaware's hundreds as TIFF images zipped together with their associated world file and metadata. Some files are as large as 23 megabytes, but most are in the 1-2 megabyte range." <http://www.udel.edu/dgs/dgsdata/hundreds.html>. I've been using them in the field in combination with my GPS unit and I can't think of a more useful FREE resource.