right now there's no real toon shader, however you can achieve some toon like effects with the skin diffusion shader. if you set the shadow smoothing to zero, you get a super hard edge which can look pretty cool.
not really a toon thing but i'm looking more close to pixar work they did. in fact, i'm trying to get a style close to presto or other creation done by pixar :)
The skin shader can be enabled by swapping from lambertian to skin in the diffusion module. Out of curiosity, what sort of features would you like to see in a toon shader?