the Singapura is a very small cat, and also very rare. I want one of those, but they're very hard to find. They are friendly, and make excellent pets. But they do take some time to adjust to new homes and owners.
the Snowshoe is also a rare breed. They are a shorthaired Birman type i think. I don't know much about them.
the Somali is a longhaired Aby. I love Somalis, it is a gentle and amiable breed. They do need occasional grooming too.
the Nebelung is like a longhaired Russian Blue, by its appearance. Its body is long, lithe, and slender with a fluffy tail. They are said to be robust and vigorous, needing only moderate grooming.
the Javanese is like the Balinese. It does not like being left alone. It has the same body type, coat and disposition as the Balinese.

That's all the information I know, hope it helps. Tell us what breed you decide to get!