"Partial list of items for sale and services the advertisement of which is not permitted on craigslist:"
"Household pets of any kind including but not limited to dogs, cats, primates, cage birds, rodents, reptiles, amphibians, fish. Re-homing with small adoption fee OK
Pet animal parts, blood, or fluids - including but not limited to stud/breeding service"

http://www.craigslist.org/about/prohibited.items