Maps
Mapping
NOAA's Office for Coastal Management has a variety of mapping tools and resources in a collection they call "Digital Coast" such as the Flood Exposure tool and Sea Level Calculator.
Mass Mapper is a statewide mapping resource (info).
Massachusetts Interactive Property Map gives tax maps across the whole Commonwealth so you don't need to dig into some town-by-town divided database.
The Merrimack Valley Planning Commission (MVPC) makes "MiMap" available for each town, e.g. Salisbury MiMap, in the Merrimack Valley.
ArcGIS is a dominant commercial mapping (GIS) software created by parent company Environmental Systems Research Institute known by it's tradename ESRI. They offer an online mapping tool at https://www.arcgis.com/apps/mapviewer/index.html
See GIS for a better overview of mapping software.
Wiki Maps
The Maps extension is included in Meza
As of 2025-07-21, using v11.0.1 See Release Notes
Boston
Boston using the Leaflet map service
Circles on Leaflet
Here's the new 'circles' feature for Leaflet maps (click to view Title and Description)