This is one of the educational ones. Greek Myth Comix has Greek mythology in stick-figure format, probably influenced by XKCD.
These can be used to teach kids of all ages about certain mythological figures or ancient Greek concepts, like Kudos or the Homeric Hero.
I especially like the Moirai and the Muses poster, I printed these out and have them on my board for reference.
Make sure you visit their store for neat merchandise or large posters.