Riley's Lock is probably the most convenient-to-get-to spot upstream from Great Falls. It might be crowded within a mile or two from the lock, but beyond that it becomes fairly quiet and peaceful. My preference is usually to go much farther out. I rode the stretch from Point of Rocks to Harper's Ferry the other week and it was beautiful, and the trail was in very good shape. Plus, there's a very cool little coffee shop in Brunswick in between. It all depends on how far folks want to drive to get to the towpath. Here's more info: The C&O Canal Bicycling Guide

Nicole, are you going to start a thread for a non-pedaling get-together?