Looking for some good maps of colonial Boston? The Doak family genealogy page has you covered. These nice folks have posted giant versions of maps from 1645, 1722, and 1775 that are zoomable. The 1722 map is especially nice for finding streets and landmarks.
You can buy paper copies from their gift shop, though the biggest copy is only 24"x30".
Here's another good map of Boston (1769).
Here's a good map of Cambridge, MA, 1760-1770.