The "best" sight-seeing package there is to see all of Boston. They have been at it for over 15 years. If you are shy, you won't be by the end of the Trolley ride. Hold on tight to your seat for you are in for a rocking good time. The driver's get you involved. Watch out for "Cheers," on Charles Street, where no one knows your name.
You can pick up the tour at any of its 16 stops. The drivers are 'extremely' knowledgeable of Boston's history and current events. The tickets are from $20-25 and allow you two days of FREE reboarding and use of their trolley's (busses).
Some of the 16 stops include the USS Constitution, State House, MIT, Boston Commons, Beacon Hill, Quincy Market, Hard Rock Cafe, and the Boston Tea Party Ship Museum.
For Freedom Trail enthusiasts, there are four stops either on or close to the trail. See the Old North Church tower where Paul Revere used his lanterns to warn of the British coming. Or see teh Bunker Hill Monument at the corner of Adams and Lexington Streets. (Not the actual location of the battle but close enough.)
Take in Faneuil Hall and Quincy Market. The hall was built in 1742 and was the meeting place of the Fathers of Independance. It was here that the "Cradle of Liberty" took place.
On Beacon Hill (what was the highest point in Boston in the 1700's) see the JFK residence, African Meeting house, Mass General Hospital.
When you visit the USS Constitution (stop 3) take the Water Taxi back to the marketplace (stop 1). It's $1.25/person, and well worth it to see the city from the water.
For the more up-to-date tourist you can go to the Hard Rock Cafe near Copley Square or visit the Aquarium. Watch out for the penguins!