Stefan Minning has 2 new filters in beta, but for Windows only for now apparently (see CGTalk discussion).
Celulight is a cel shader and normal map generator for AE, and uses drawn outlines or cels as source files and allows them to be lit in a pseudo 3D environment using AE’s internal lights. Possible styles include: Classic toon shading, Modern 2.5D Toons, and “Kingdom Hearts” Styles.
Floodgate "can be considered an advanced paint bucket or fill tool" which "floods up to 64 distinct areas with up to 8 different colors. Floodgate is squarely aimed at coloring in toon and cel animation and outlines drawings, which is a real pain to do in After Effects without it."
Update: these might be fun with Live Trace versions of video...Aharon Rabinowitz had a video tutorial series on this feature, Converting Video to Cartoon.
Update 2: there's a report in comments here that this filter has problems in AE8.