Roadside America is an online guide to the third category with some secondary sites thrown in for good measure. Sites like a 1880s robotic cowboy town right outside Sioux Falls, South Dakota; a schismatic Virgin Mary site in Wisconsin, and dinosaurs versus the Union army in Virginia are just some of the oddities on the website.
Navigation is primarily done on a map allowing one to view sites by state. Other great features can be viewed in video clips or a list on how Americans view various countries.
So next time you are going on a trip check this site out and plan a detour to the weird!