Keeping a pet ferret in New Jersey requires a permit from the Department of Fish, Game, and Wildlife. Information and applications are available when adopting a ferret from the shelter. NetVet Ferrets provides links to numerous ferret sites.
The Gerbil Information page is the English version of a gerbil site from the Netherlands.
The Guinea Pig Compendium is a good place to start for information on cavies. Guinea pigs are often available for adoption, too.
The best site we've found for rabbits is The House Rabbit Society. It covers all aspects of rabbit behavior and care. We almost always have rabbits available for adoption at the shelter. They must be spayed or neutered before leaving the shelter.
We occasionally have other animals for adoption, most commonly pot-bellied pigs, chickens and roosters, mice and rats, iguanas, turtles, canaries, cockatiels, and parakeets.