Animal Planet — May not include all of the breeds, but certainly has nice pictures and descriptions on several.
Cat Fanciers’ Association (CFA)— The CFA was established in 1906 and is the largest registry of pedigreed cats. It’s mission is to preserve and promote pedigreed breeds of cats and to enchance the well-being of all cats. The website provides a wealth of news and articles.
Cat Time — A good place to explore “all things cat”. Aside from a comprehensive list of breeds, they also offer cat facts and videos.
Pet MD— Offers a “Cat Breedopedia” that was authored by veterinarians.
Purina — This pet food giant focuses its listings on helping to choose which breed is right for your household. Breed offerings can even be filtered by various common traits and tendencies.