First, ask around and see if a trusted relative, neighbor, friend, or coworker would like to take your pet. You can also contact reptile clubs and local pet stores to see if they know of anyone who is interested. If you purchased your turtle locally, ask the store that sold it to you if they will take it back. Some reptile clubs and groups do have rescue and adoption programs; however, the number of animals they can take in is usually limited, and they may not be able to take in some species at all. Advertising in the newspaper and on internet sites such as craigslist tends to generate a lot of responses, though you will need to be more on-guard against impulse buyers and scam artists who hope to make a quick buck by reselling your pet or its equipment. As a last resort, you can always relinquish your pet to an animal shelter that is willing to accept it. But please, under no circumstances should you ever release any pet turtle into the wild! Not only is it illegal to release any non-native or long-term captive animal, this practice more often than not turns out to be a death sentence for an animal that is unaccustomed to living in the wild, or not adapted for living in that environment. And the ones that do survive may crowd out or hybridize with native species, introduce diseases that native species have no natural resistance to, and otherwise wreak havoc on the local environment.
Rio Grande Turtle & Tortoise Club