Over on one of the MLing boards there has been a lot of playing around with alternates because of the Republik's latest BS lead ban. Glass marbles, wooden balls, rubber no-bounce balls, etc. Not all are available for every bore size at present - in fact they are all pretty limited with only a couple of bore sizes of each so far. While some might show some promise, most failed miserably even for just target shooting let alone hunting.
I lived and hunted in the last main CA stronghold of the condor's back in the late 60's to mid 70's (Carmel, Monterey County), and I'm not convinced there really is condor's in all the areas they put under the lead ban. There are less than 150 condors total currently (April 2008) in the wild between the Grand Canyon and the coastal mountains of CA and Baja, so the CA ban includes historic range in that state whether they actually have wild condors flying there too or not.
I saw the error of my ways and got out of CA in 1976, and won't be ever even visiting that state again. But they are migrating to and taking over many other states with their foolishness now days. Like has been said, with 175 pounds of lead and full sets of molds for every bore I shoot (with backups) I'll be shooting lead until I die.