http://www.usatf.org/routes/map/
I was using mapquest to check distances and it was very ineffective considering I don't always run on streets. This makes it really easy to keep an accurate log, and would even make it possible to run some sort of interval workout over a long distance if you can remember markers and distances.
Overall, it's a great find. The running club here at school sent the link to me and it helps a lot.
Hope you find it helpful!