This is really nice, but I wish there was a way I could add more locations to explore. I'd love to do this to my own city. I've tried exploring and hacking in my own links, but it's pretty obvious that the data was only preprocessed for the cities shown in the list.
Just want a text box to let me tell it where to go essentially. I realize I could just download the source and run it myself.
Edit: Should have headed to Wikipedia first: http://en.wikipedia.org/wiki/Shortest_path_tree