Most video codecs are optimized for movies. However, not all videos look like real-world movies, and usual codecs do not aways give good results.
So are there methods specifically designed for cartoons/animated screen captures? Are there any open-source implementation?
I would assume the Tech Smith Codec as used in Camtasia and Snagit) would be a good choice.
Cam Studio appears to be open source - I assume their codec is also.
i once saw a 2h cartoon movie (manga) encoded with theora, which they somehow got down to ~150MB and still extremely crisp - even in fullscreen (dion't ask me how they did, but that must have taken a load of tweaking)