To stick everything in one place, here are the Mudcatters I could find. In no particular order:

Sandy & Caroline Paton
Saturday 1:45pm Natick Room: Folk Songs for Families
Saturday 7:45pm Lyric Room: Favorite Songs & Ballads

Judy Cook
Saturday 5:00pm Chorus Room: Ballads of Ghostly/Supernatural Lovers (as part of Sue West & Friends)
Saturday 8:30pm North Star Room: The Family in Song
Saturday 9:15pm Lyric Room: Trickery & Persuasion
Sunday 12:15pm Lyric Room: Sun, Moon, & Stars (as part of Suzanne Mrozak & Friends)

Kathy Westra
Sunday 12:15pm Lyric Room: Sun, Moon, & Stars (as part of Suzanne Mrozak & Friends)

Dan Milner & Bob Conroy
Saturday 5:15pm Music Room: The Port of New York
Saturday 6:45pm Music Room: Shanty Sing (as part of Dan Milner & Bob Conroy

Dan Milner
Saturday 3:15pm North Star Room: Songs Celtic & Not (as part of Boston Celtic Singers Club)
Sunday 10:45am Lyric Room: The Naked Voice (as part of Jerry Epstein & Friends)

Deb Cowan
Friday 10:00pm North Star Room: Songs of Hattie Mae Tyler
Saturday 3:15pm North Star Room: Songs Celtic & Not (as part of Boston Celtic Singers Club)
Sunday 11:30am Natick Room: Silly Songs & Funny Folk

The Johnson Girls
Saturday 2:30pm Lyric Room: Maritime Music for All
Saturday 6:45pm Music Room: Shanty Sing

Animaterra Women's Chorus
Saturday 10:00am Small Hall: Sing for Joy

Woodchucks Revenge
Saturday 12:30pm Music Room: Laugh It Up!
Saturday 8:30pm Small Hall: Old Country Song Swap

Boston Celtic Singers' Club
Saturday 3:15pm North Star Room: Songs Celtic & Not

Ukelady
Friday 10:00pm Lyric Room: Sing and Swing
Saturday 12:30pm Music Room: Laugh It Up!
Saturday 2:00pm Small Hall: Elegant Round Singing (as part of Sol Weber & Friends)
Saturday 7:45pm Natick Room: Rounds Concert (as part of Sol Weber & Friends)
Saturday 9:15pm Natick Room: Carter To Country & More (as part of Triboro)
Sunday 3:00pm Small Hall: Round Singing Jam