Yeah, what he (ishoot4thrills) said; I've had good luck with the Quivit (or however you really spell that) silencers from Alaska Bowhunting Supply. Cat whiskers work well too, but they reduce string speed more than the wool, etc.
There's an article from earlier this year in TBM written by Paul Bender who did a study on various silencers and if memory serves, concluded that the hush puppy style was the best combination of light weight and silencing. Cat whiskers, I think, were the most effective, but also took the most speed from the string.