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.