Roads affect us all: they displace land, trees, and people, they take long to plan and build, and often millions (or billions) of dollars are involved. Since humans build them, the projects are prey to all the grandiose dreams, kickbacks, civil disobedience and corruption that accompanies other social issues. Every road has a story behind it, and chances are you'll find one here that's close to home.
For roadgeeks, there's plenty of stuff to hack: how roads get their numbers; what system of "secret routes" a state might use; what's coming up next year; what was decommissioned before you were born.
You can do this too! If you have an area of knowledge or interest, put up a site, or otherwise get involved. The AARoads Forums are a good place to meet others.