Polydactylism
Catteries, Personal Pages, American Polydactyl, Cat Fanciers' Association: Online Magazine fo, Ernest Hemingway's Home & Museum, Polycat, Polydact Cat FAQ, Polydactyl Cats, Polydactyly, The Straight Dope
Bobtailed and Tailless Cats
Article about congenital tail anomalies including Manx, Bobtail/Pixiebob and Curly tails.