Here we go yet again. Feel free to chime in on the...
NCR (Northern Central Railroad Trail)
The Northern Central Railroad Trail (NCR), aka The Torrey C. Brown Trail, is a wide stone dust surface trail extending 20 miles from the Hunt Vallery area all the way to the MD state line. At the MD state line you can continue on the York County Heritage Trail another 20 miles to York, PA. It is important to note that the trail surface changes as you cross into PA.
The trail is well used by hikers, joggers, bikers and there is also access for fishing and tubing.
If you plan to visit the trail, and I recommend that you do since it is a great ride, you should note that the trail is heavily used on weekends and the parking lots are frequently crowded. The northern end of the trail is less crowded during peak times.
More information: http://en.wikipedia.org/wiki/Torrey_C._Brown_Rail_Trail