Hey I just saw this article in the New York Times and thought it was pretty neat. Apparently there is an old, un-used section of an expressway that people bike on, and part of it will formally converted into a "Bike Pike". The article doesn't say how long the total un-used section is, but the "Bike Pike" looks like it'll be about 20 miles or so. There are also two 1 mile tunnels that you can ride through in total darkness.
It's out near Breezewood PA. Just thought I mention it. Looks like a neat place to ride.