This one came out last week, but it’s cute, and we haven’t seen it mentioned a lot yet. Lighting artist Luca Fiorentini has released nEyeMaker: a fully procedural Maya eye with a nice GUI to control appearance.
As well as standard aim and pupil dilation controls, the other parameters – 27 of them, ranging from iris spot frequency to the angle of veins in the sclera – should give you scope to achieve pretty much any look.
As the video above demonstrates, the set-up will handle animal and monster eyes, too. It’s designed for mental ray, but you can bake out the textures and use it with the render engine of your choice.