Posting on craigslist (or anywhere else) to give away any animal is one of the most irresponsible, and careless things anyone could do as a pet or livestock owner. In my area there have been confirmed cases where different people, who may dress, act, and speak well, go around taking the "free to a good home" cats, kittens, dogs, puppies, etc, and then using them as bait animals for dog fighting operations. I'm sure that this happens elsewhere too. Ask your vet, or any vet in your area, if it is possible for it to have a good quality of life. If it can, then ask them, or the local humane society, or any rescue group for help in finding the little one a home. If it can't have a good quality of life, then ask the vet to euthanize it. The vet is a professional, and will be able to accomplish that painful task with professional expertise, and with the chick's well being in mind. Home (or online) ideas for euthanizing it are not the way to go. Look at it like this...how would you want to be treated in a similar situation?