American:

I find this genre the most interesting because it is comprised of a lot of <i>different</i> styles. Take South Park for instance. All of the characters are outlineless with big round eyes and there is no shading. Robot Chicken on [adult swim] is just doll animation comprised of pointless, yet funny objectives. The Simpsons are a funny, long running series created by Matt Groening with yellow-colored characters getting in all sorts of weird situations mostly worked out by the end of the episode. There are definitely more, but I'm not in the mood to cover them all.

British:

I'm not sure that I've even really heard of any interesting cartoons from the UK. I'll have to get back on this.

Japanese:

Now this is a genre! This one packs more cartoons than I've ever seen, yet still doesn't make up for how many are exported of the US each year. Cartoons (or anime) such as Inu-Yasha, Pokémon, Tsubasa, Ranma 1/2, Tenchi Muyo, Bastard, Big O!, Paranoia Agent, Chobits, etc. I could go on, but who really wants to hear them all?

Internet:

Now, I don't really know what to say about this one. There is probably more animation on the Internet than in the mainstream public in any part of the world combined. It ranges from 2-bit pixel animations to full-length movies! You never know what you can find on it!

P.S. I just posted all of this because I have really nothing else I can think of…