The library has been gifted with a printed index covering the 1800 Federal Census in Massachusetts. The 9-volume set covers all the counties that existed in 1800 (Franklin and Hampden were established later, and their towns are presumably included in the volume for Hampshire County). The volumes were delivered to the Library personally by the compilers, Rebecca Sullivan and Deborah Larsson.
Each volume lists the towns of the county in alphabetical order in the first half of the volume. In the second half, the entries are resorted by name to facilitate finding names of interest. Each entry carries the same information: Town, Head of Household (named), and enumeration of "free white males," "free white females," "all other," and "slaves," plus a "Total" column. ("All other" might include free non-whites or indentured servants?) Flipping through the volumes I noticed that there were few "slaves" or "others" but they did exist. In the Bristol volume there is apparently confusion between the "slaves" and "total" column.
The compilers caution that the condition of the original documents is sometimes compromised, so the entries may not be entirely accurate. While nothing beats a look at the original, we hope that you may find this a helpful tool in seeing a snapshot of your ancestors' town in 1800 Massachusetts.