Give a listen to anything done by the former Invisibl Skratch Piklz. Pick up Q-Bert's "Demolition Pumpkin Squeeze Musik" in addition to Wave Twisters (imo it's a bit better). A new group to watch out for is Ned Hoddings. They opened for D-Styles' "A Night at the Knitting Factory" performance and seem to be the most innovative purist scratch group at the moment.
Asisphonics.net has some good articles and guides on the progression of scratching if you're interested.