Probably to PETA which then euthanizes them and throws the dead animals in other people's dumpsters. PETA was found guilty of littering because of this. They were not found guilty of animal cruelty because there was no law against euthanizing healthy animals which is what PETA was doing.
Dr. Proctor later added in The Virginian-Pilot: "These were just kittens we were trying to find homes for. PETA said they would do that, but these cats never made it out of the county." [0]
[0] http://www.petakillsanimals.com/trial
Also: http://www.thisistrue.com/peta.html