This page lists other digital map collections. These are external resources, each with their own search tools. This is not an exhaustive list, but rather collections relevant to those interested in Boston/New England or historical maps in general. See the links at the end for more comprehensive lists.
Digital Commonwealth (includes all Boston Public Library digital material)
Historical Map Web Sites
Perry-Castañeda Library Map Collection
Index to the Largest Map Image Sites
Maps, Globes, and Plans: An Ongoing Census of Free Digital Archives
Atelier Ideas and Research