I recently came across a new cat litter that is eco friendly. It is called FreshAire and is carried exclusively by PetSmart. It is made up from a combination of pine, Montmorillonite clay and Bentonite clay. Although I still plan on using the Dr Elsley's in one litter box, I plan on using this one in the other.
From reading the FAQ's page on their website, I was suprised to learn that there are practically no regulations in place regarding proper labeling of ingredients that may be contained in cat litters. Which means that various substances, such as synthetic fragrances, PTFE-style dust suppressants or synthesized anti-microbial agents, might not be listed on the package. http://www.freshairelitter.com/FAQ.aspx