What is the best way to get rid of a couple of propane tanks
@tflea :
You could probably contact a local propane supplier and they'll most likely buy the tanks from you for a nominal amount...Tanks are like a "core charge" in the automotive parts industry....If you have a tank, you "trade it out" for a filled one and pay only for the gas...If you don't have one, you pay for the tank and the gas....
As for "recycling", I think you can recycle them as scrap metal if certain conditions are met(the tank is drained and it's fill valves are removed, etc)....But not sure...