It's a video game, but the art is anime-ish.

Her name is 'Tabby', so it fits there too.

http://dothack.wikia.com/wiki/Tabby

Look! Shiny URL!

I don't know whether they count, not having seen the show.

The focus of that's more on the boys than the girls, but still. There's Yuiko Hawatari- a classmate of the main character's, Ritsuka Aoyagi-, Hitomi Shinonome- their teacher-, and Osamu Kimizuka- a friend of Ritsuka's from his previous school who's only appeared in one sidestory, pretty much.

Or if she counts, there's Tabby from .hack//Roots, I guess.

Found this on the net: http://en.wikipedia.org/wiki/Listofcatgirls

Might take a while to look up all those different people, so I'll give you a few catboys to go along with it.

Hellsing has Schroedinger. He'd probably be the most adorable thing ever to walk the multiverse if he wasn't an arguably insane Nazi kid. Despite that, he looks like something you just wanna pick up and cuddle. It's kinda creepy.

If you're willing to accept anthropomorphic cats, there's also Neko-sensei/Mr. Cat from Princess Tutu. He's a pretty funny guy, and rather obsessed with marriage.

I'm not sure if this last one really counts, seeing how he's from a webcomic instead of a manga. The fairy tale webcomic (sort of) No Rest for the Wicked features the catboy Perrault as one of the main characters. I'm not certain about the status of webcomics in this community, though, so he may not be a legitimate cameo.

But she doesn't have a tail or ears. She does have cat eyes though and very cat-like mannerisms. Of course, if you just want the ears there's always Chii from Chobits (not technically a catgirl, but...).

First one I thought of. She's from Outlaw Star.