For the USFWS approved list of non-toxic shot circa 2006 see:

http://www.fws.gov/news/NewsReleases/showNews.cfm?newsId=45735D9B-65BF-03E7-2A3B0D75A0A06180

For very interesting (but 1990's dated) microscopic images and descriptions of some of the non-toxics then, see:

http://www.lab.fws.gov/shotpellets.php