DNR “Tons of Maps Online” or ToMO service. Here you can browse every USGS 1:24,000, 1:100,000 and 1:250:000 quadrangle for Minnesota. This is currently an experimental application at the time of posting. See http://maps.dnr.state.mn.us/tomo/
The Free GIS Data Blog encourages you to visit www.GISuser.com for more leads to free GIS data!