Tracy Butler writes this totally awesome comic called Lackadaisy Cats (100% recommend it, great art & fun story)
Anyway, she just threw up a tutorial on facial expressions, lot of great stuff in there. Here's a teaser (thought my fellow animators would appreciate this one). Run and check out the whole thing.
She seemms to be coming at it through pure intuition. Getting to the same place, but from the opposite direction as Ekman & Faigin. She also is doing that Preston Blair trick of drawing the whole eyeball, then occluding it with cheeks and lids.