This year, we're doing the usual 3 1/2 day bike trip up the C and O Canal Towpath trail (183 miles) from DC to Cumberland, with an added 150 miles from Cumberland to Pittsburgh for those interested in extending the trip a bit. The plan is to leave DC on Thurs, 23 July afternoon (meet up around 4:30PM), with the Pittsburgh people coming in that day or the night before. Leaving DC after work, we will do about 20 miles on Thursday, about 60 miles (each) on Fri and Sat, and the remaining 40 miles of the Canal on Sunday. From Cumberland, anyone heading back to DC will catch a ride (pre-arranged outfitter) back to DC, so that they will be home at a reasonable time for work the next day. Anyone heading further on towards Pittsburgh will continue for another 2.5 days (60 miles/day average).
I have biked the canal 7 times, and it is a delightful bike trip.... the path is level (except for 10 ft rises at each lock) and is packed dirt/gravel... yes, you are in the woods pretty much the whole time, which is nice, but there are small towns every 30 miles or so where you can eat or restock. The Canal is a National Historical Park, so it is well maintained and there are *free* hiker/biker campsites (clearing with well water pump, porta-potty, picnic table, and fire pit) every 10 miles or so. Additionally, there are many interesting natural/historical sites along the canal that make for a fun break from biking.
I've only done the GAP twice, but this section is also great - the trail is smoother and has more towns than the Canal, but is still in the woods. The GAP also features the "easiest" (note: relative term) 2000 ft climb you will ever do, a number of tunnels, the Mason-Dixon line, and the Eastern Continental Divide.
For this trip, it sounds like there will be a large Pittsburgh contingent and a generally large group. Hopefully, we are looking at a big rolling party - don't miss out!