After a quick test on a nasty cassette and chain, soybean-oil-based (which means biodegradable and non-toxic!) El Duke (pronounced El Doo-kay) degreaser rocks it. Makes gakked up parts shiny, smooth, good.
Sorry Park, but El Duke is my new way to get stuff clean. It's solid. Plus, a dog with a bone logo is unbeatable in itself. You know how we do.