I do not know of any web sites devoted to Shaker music. Gourd Music, in Felton, CA., has a trilogy of CDs available containing Shaker material. They are entitled:
Simple Gifts
Tree Of Life
Music On The Mountain
The artists here (that word artist is so over-used…but in this case, deserved) are William Coulter/Barry Phillips and friends…
I have been involved in recording sound and music of all kinds for a lot of years, and I feel this trilogy is among the best example of well-recorded acoustic music I have heard. Although I have never checked, Gourd may publish the scores to one or more of the CDs.
Cheers to you.
Byll