"Bike the C & O tow path from Cumberland... " a Cumberland Travel Page by IngaRita

Biking from Cumberland to DC sounds like a ton of work but actually its not. While I was on the trip people would ask me mostly logistical questions...how did you get to Cumberland?...where did you stay?.. what did you eat? So first, go to this website and read about the trail: http://www.bikewashington.org/canal/index.php
This really has all the information you'll need to prepare and carry out your trip. I didn't even need to consult any other websites. I thought about buying a guide but realized that it didn't really have any extra information in it that I couldn't get through this website.
Call several campsites and make sure its not biker week the same time you are planning to go.

The next thing that I did (and wish I did more of) is take some small rides. If you live in DC or near the tow path, try to get some miles in riding on gravel. After Georgetown and a 10-mile stretch on the WMRT you'll be on gravel the entire time.
As far as the kind of bike to use...i used a Kona Jake cyclocross bike which was perfect. My tire size was 700x35c. I did see people on mountain bikes (which is a little over doing it) and roadbikes with the widest tires you can get on. Here is a list of my bike gear:
Double rear panniers. I had Transit dry bags, which are essentially just large dry bags. I thought it would bother me that I didn't have pockets but it really didn't matter.
Lumbar pack. I like my lumbar pack but it can be a little cumbersome on the bike. The pack took the place of a handlebar bag. I didn't want to spend more money on purchasing a handlebar bag. I used the lumbar pack to carry my camera, wallet, snacks, extra maps, and coffee cup :) .
Water bottle cages, 3 inner tire tubes, equipment to change a tire, bike pump, bell, front bike light, helmet, bike computer, bike lock.
I camped out during the trip. Here is a list of everything else I brought:
tent, sleeping bag, pad, stove, fuel, pots, sunscreen, bug spray, chacos, tennis shoes, 2 pr bike pants, 4 shirts, underwear, socks, bottom and top to sleep in, shorts, 3 t-shirts for after ride, bath suit, book to read, headlamp, toiletries, quick dry towel, camera, phone, chargers for theses, money, ID, poncho
As for getting to Cumberland. This was the most stressful part. You have some options...get a friend to drive you (you must have really great friends!), rent a car, have a service take you. I called Charles from the company Freedom Trail Riders. I was going solo and he didn't have anyone else to pick up that day which was a little problem. Thankfully he was heading to western Maryland so he could take me. The website quotes $130 but he asked for $80. I didn't wheel and deal because I was just thankful that I finally had a ride.

Day 1 - 184.4 - 140.8 mile post. Cumberland to Little Orleans Campground. The trail starts in Cumberland right in front of the visitor's center. Go down the trail and turn left. You can get most of the info that you need from bike washington website so I'll just talk about extras that aren't mentioned there. Or stress details that you should know about. I brought my lunch and ate on the trail. I did bike around in Oldtown, MD and rode across the single lane bridge into WVA. At mile 156.2 you'll get to the Paw Paw tunnel. Its a very long, dark tunnel and I was actually pretty scared. Bring a bike light! At 140.8 turn off the trail. Follow signs for Bill's Place. Little Orleans Campground is at the top of a very large hill. I had to get off my bike and push. It was $25. Has a camp store, shower's included and pool that was closed due to the torrential downpour that I just road 10 miles though. I would have liked to check out Bill's Place but didn't feel like climbing the HILL again!
Day 2 - 140.8 - 99.4. At 124.4 stop off at C & O bikes. They have a cool bunkhouse that's $10. It was right in the middle of my day but looked like a good overnight stop. I biked around Hancock a little and ate lunch at the Lockhouse Restaurant. I think to get back to the trail I retraced by route. During this leg I hoped on the Western Maryland Rail Trail (hardtop) that runs along side of the C & O. At 112.4 I turned right off the trail and headed into Fort Fredrick. Pretty cool, but not a whole lot there. At 99.4 I head off the trail in Williamsport. Turn left of the trail. Turn left next to this barn looking thing onto W Potomac. At the light (Conococheague St/68). I had dinner at Tony's pizza which is on the corner of Salisbury. Continue on 68, under 81 and eventually you'll see Jelleystone on your right. $32/night. Heated pool, nice showers. The people where really nice here. I had a whole camp area to myself. Lots of families here.
Day 3 - 99.4 - 58. Very Important! To bypass the whole Bike Detour of the C & O and see some cool countryside turn right when you leave the Jelleystone. At the blinking light turn right. For about 7.5 miles head downhill toward the potomac. When you feel you are lost ask someone where the Potomac is. This is when I ran into a nice old man who was biking his Schwinn to Indiana. He unfortunately only had one gear left and it was the hardest one. I didn't do the optional 22-mile Antietum ride. At 72.8 I crossed the river towards the Bavarian Inn to get to Shepherdstown. Very quant old town. I had lunch at the Stone Soup Bistro. At 58.0 to get to the Harper's Ferry I turn off the trail. At the road head left and go up a long hill. At Sandyhook Rd turn left and head down a steep hill. Hostel on the left. $10 to camp, $21.20 to stay in bunk house. I camped. For dinner I got carry out from a restaurant that Carol (hostel propriertor) recommended. Turn right out of hostel, turn left at stop sign, so down hill and its on your right across the street from the liquor store. Behind the hostel is a path (hike) that takes you down over the RR tracks and to the C & O. At the trail turn right and when you get to the overpass head down towards the Potomac and go for a dip. You won't regret it!
Day 4 - 58 - 0. Retrace back to the C & O and head left. AT 48.2 turn left off the trail and turn right. Go to B & S minimart for some good food. Sandwiches, fried chicken, cold drinks, candy. At 14 leave your bike on the path and walk into Great Falls, very pretty.