At least if you're a fan of Historical Markers like I am that ties local/regional history to place. I stumbled upon this site as I was beginning the arduous (not really, I very much enjoy) task of planning another ride for next year's Wildcat Mountain Rally.
In looking for various historical sites and markers in the area of SW Wisconsin that we ride through, 'a few links later' found me at Historical Markers Database (hmdb.org). Lots and lots of info there but the thing most surprising and something I'll make use of on various rides in the future is the ability to use the GPS function on the Smartphone that I carry (thanks to my employer) to locate nearby historical markers. Punch up the website, activate your 'location services' on your phone and a list will pop up of your current area's historical markers including distance away. Not only are there links to detailed background information, but also included are maps of exactly where the marker is, most often with a photo providing another clue as to the marker's exact location.
The website is hmdb.org, but if you're logging in with a smartphone, you can get directly to the Mobile Function of the website at http://www.hmdb.org//mobile.asp