A good Dover reprint:
"The Gift to be Simple," Edward Deming Andrews, $4.75. Eighty songs in notation.

A little information in threads 5527, 21813, 7307.

The Shaker Journal Shaker
A good introduction, and defines the difference between Shaker hymns and songs. Also a brief list of sources, discs, etc. (I would copy before it is taken off- looks like most of the site gone already.

Some anthems by Hampton here: Golden Plates

An excellent cd: "Simple Gifts," the Boston Camerata, Erato 4509-98491-2. List and notes here: Simple Gifts cd

Just a few. There is an online site with a few songs and good discussion that I will have to look up.