Here's a link to hydrocarbon refrigerant replacements. It's a grey area as to the legality of using this but the argument for it being legal is as follows: R134A is not classified as an ozone depleating element so the replacement of it is not controlled by the same agency as R12, which is. On the other hand, it's flammable.
I gotta admit, the idea is attractive. I'm not that worried about flammability. Heck, the car is full of freak'n fuel anyway.
mpnye, do you have any experience with these producs?