A couple of late additions:
Marina Oliver's single freebie is the presumably non-shapeshifter contemporary romance:
Mating the Llama
Sylvia Engdahl (
ISFDB entry) offers Books #1 & #3 in her self-published YA SF "Flame" series free to download or with coupon. She's also got 50% off a non-fiction book on historical cultural views of astronomy, originally published by Atheneum in 1974, and her imprint
Ad Stellae Books also offers 50% selected historical YA fiction works by her late mother.
ETA:
Phoebe Matthews (
ISFDB entry, though mostly known for pseudonymously writing romances for Avon) has some free fantasy/sf/paranormal stories and 50% off several titles.
Lorraine Bartlett offers a freebie of an omnibus edition of her first two Five Star-published Jeff Resnick mysteries, and 50% off selected titles.