MassGIS maintains a comprehensive, statewide database of spatial information for environmental research, planning and management. You can read an overview of what MassGIS offers here: (http://www.mass.gov/mgis/dd-over.htm).
Two types of data are available from MassGIS: Vector data and Image data. They will be discussed more explicitly in the following sections, but here are the basics.
Vector data are available as ARC/INFO Export Files (.e00) and ESRI Shapefiles. You can download them here http://www.mass.gov/mgis/dwn-vect.htm. Spatially, they are provided at multiple scales:
MA town
USGS quad
Orthoganal Photo quad
Basin
Watershed Area
Soil Survey Area
There are also indices that reveal the organization of these files. They are listed as follows:
Towns Index: http://www.mass.gov/mgis/ix_town.htm
USGS Quad Index: http://www.mass.gov/mgis/ix_quad.htm
Orthophoto Quad Index: http://www.mass.gov/mgis/ix_oq.htm
Basins Index: http://www.mass.gov/mgis/ix_bas.htm
Watersheds Index: http://www.mass.gov/mgis/ix_wat.htm
Soils Index: http://www.mass.gov/mgis/st_soi.htm
Image data consists in MrSID and TIFF formats. You can download them here:http://www.mass.gov/mgis/dwn-imgs.htm. They are spatially organized as:
USGS topographic quad maps
Orthophotos
You can find complete list of available layers at this link: http://www.mass.gov/mgis/laylist.htm.