If you’re excited about maps, you have to check out the David Rumsy Map Collection. This 30 year project has amassed over 150,000 maps and has been using high-resolution scanning to digitize the collection. The digital maps are available for free non-commercial use through a Creative Common License, making this a great resource when you’re looking for basemaps or historic information.
One of the cooler features on the Rumsy Collection website is the georeferencer. In the georeferencer you can select a digitized map from their collection and overlay it on another map to better compare the two. Happy exploring!