While I focus on Universalist worship resources, the book digitization revolution has brought back to light Unitarian service books, too -- by which I include comprehensive prayerbooks and other resources (often with hymns) that have service elements.
- The Altar at Home; selections and prayers for domestic worship (1869; 2nd series) by James Perkins Walker.
- Order of Morning Service and Selection of Psalms for Channing Church, Newton (1892) by George H. Ellis.
- Church worship: in readings, songs and prayers (1892) by Third Unitarian Church, Chicago (Google link)
- Five Services for Public Worship with Services for Special Occasions (1895) by American Unitarian Association.
- Services of Worship: Used at the Church of the Unity (Springfield, Mass.) (1895)
- Book of Common Worship (1913) by American Unitarian Association.