Well, I have run across some sites for catgirls/boys, though they are pretty clean unfortunately. But, I figured I would post them up just because the pictures are good, and because they do contain *some* hentai.
http://www.bewildered-art.com/catgirls/index.html -this is all art by the same artist and is totally catgirls if I'm correct. There is one section dedicated to hentai here, though most of the other sections are risque at best.
http://www.geocities.com/neo_neko2003/ -ok. This is where to go if you want *clean* catgilrs/boys. The pictures *are lovely, but they are still clean. That's the only thing I can offer 'till I get the hang of lj cuts...sorry!!