If you live in Manchester (NH), you have no excuse not to make it to Boston at one time or another. You have several easy transportation options that don't involve getting lost on construction detours or trying to figure out narrow, one-way streets.
Today we took the bus from Manchester to Boston (www.concordtrailways.com/concord_trailways.htm). We drove 15 minutes to the bus station and dropped our car off at the parking garage next door (see www.cnhparking.com for rates: $6 for 4-10 hours, max $8 per day). Two round trip bus tickets cost us $20 each. There was no problem getting tickets, no line and the staff were friendly - but in today's security conscious world, even bus passengers need to show a photo ID to purchase tickets.
We chose the 9:30am bus. It was clean, the driver was alert and friendly, and the rest of the passengers were quiet. There was plenty of space on the bus which drops you off at the South Station at 10:30am with plenty of time to spend the day in Boston. The South Station is a transportation hub that services Amtrak trains as well as buses and shuttles to Logan Airport as well. It was very easy to pick up a ticket for in-town transfers.
Like any large city, there are a ton of things to do in Boston but today we chose the Fine Arts Museum. We had a very nice lunch in the cafeteria before walking around some of the American exhibits. We left the at 2:30pm and just missed the 3:15pm bus coming back home. It wasn't a huge problem, we simply caught the next bus which left at 3:45pm and made a quick stop in Londonderry; it was filled with commuters getting off at the park and ride lot. We made it back to Manchester a little after 5pm. After a nice day in Boston we had a fine dinner at Fratella's in Manchester.
For $46 in transportation costs, my wife and I had a nice day in Boston.