This is something we did last summer to start the Transam and I think it's worth writing a quick thread about it to give some options to future Transam-ers. We flew into Baltimore, stayed a couple of days in DC and then rented a car to drive out to Ocean City, MD. It was a short ride down to Assateague Island where you can camp on the beach. Makes for a beautiful start (or ending) to the ride.
From there we chose to cross the Chesapeake Bay by ferry, which required crossing the Delmarva Peninsula to Crisfield and hopping on a ferry which goes from Crisfield, MD to Reedville, VA via Tangier Island. See here for ferry schedules.
Here are my notes from MapMyRide:
Take adequate supplies of water and food. We had to stop at a house to ask for water but this could be avoided by making a detour into Snow Hill (next to the 28mile marker on map my ride). The junction with Highway 13 near Pocomoke City has a liquor store for snacks and drinks. If you want anything else you could head into Pocomoke City itself. The short stretch on highway 13 (Ocean Hwy) is quite busy if I recall correctly, but it's only a short stretch. Camping is available at Janes Island State Park in Crisfield.
The problem with this route is the US-360 bridge. It is not cyclist friendly. There is no shoulder and it is 1 mile long. We intended to camp just before the bridge and ride over early in the morning or around 10-11am to avoid rush hour. We missed the turning and ended up riding over the bridge into Tappahannock. Two of us went as fast as possible and the other guy held on for dear life and caused quite a tail-back behind him but we all survived. Bear in mind that we are young, stupid and used to cycling in a land where cyclists aren't given loads of space (UK). If you cross at a sensible time it might be worth taking up the entire lane and enduring some horn blasts - use your own judgement based on traffic and how much space the drivers are giving you.
When you reach Tappahannock pop in and see Donald Mayhew at Mayhew's Antiques on the right before the main junction. Donald and his assistant Karen would love to see more touring cyclists. Tell them the Lads on Tour from the UK say hello!
There are motels available in Tappahannock, but no camping as far as we were aware. There are supermarkets if you fancy stocking up on breakfast bars and bananas. MapMyRide also shows a bike shop should you need one.
The route from Tappahannock to Mechanicsville was picked based on AADT traffic figures and could be improved quite a bit. Services are limited so take plenty of food and water and be prepared to ask for water at houses. Alternatively you could just take the 360. Street view shows that it has a shoulder so it could be fine but ask the locals and check for yourself. http://www.mapmyride.com/ride/united...24068945498306
See your Adventure Cycling maps for services/camping/motels etc. in Mechanicsville.
Hope this helps. Any more suggestions would be welcome to help future Transam-ers.