Haddam Historical Society
- News, events and information on research, collections, education and the Thankful Arnold House.
- http://www.haddamhistory.org/

Society of Descendants of the Founders of Haddam
- Membership organization that promotes the research and documentation of the history of the town.
- http://foundersofhaddam.org/

Higganum Congregational Church
- Information on church staff, activities, worship and church school.
- http://www.hccucc.org/

The Haddam Neck Congregational Church
- Vintage and contemporary photos, church overview, upcoming events and contact information.
- http://www.haddamneckcongregationalchurch.org/

First Congregational Church of Haddam
- Pastor's message, calendar, sermons plus information on education and church services.
- http://www.haddamcongchurch.org/