| Name | Deductibility Code |
| Complex Systems Optimization Laboratory Inc. | -- |
| Country Dance & Song Society Inc. | 1 |
| Friends of the Hilltown Cooperative Charter School Inc. | -- |
| Horse Mountain Institute Inc. | -- |
| Massachusetts Charter Public School Association Inc. | -- |
| Meekins Library Corporation | 3 |
| Williamsburg Historical Society Inc. | -- |
| Williamsburg Trails and Greenways Association Inc. | -- |
| Williamsburg Visiting Nurses Association | -- |