http://www.mob-rule.com/ allows a user to track the US counties they have traveled to and produces a nice map of the results.
I have a traveling goal of crossing all the US state land borders. For example, to complete the state of Idaho, I would need to cross the WA/ID, OR/ID, NV/ID, UT/ID, WY/ID, and MT/ID borders. Is there something similar to the link above for tracking the state lines that someone has crossed? Ideally it would in some way "color in" a border once you've logged that you've crossed it.