Minecraft wiki entry for Skin, associated text: The modern layered skin template; every body part can have a second layer.
An adaptation of the previous template, color-coded to match the appropriate faces of the skin: front, back, left, right, top and bottom. The checked areas represent the secondary layer.
A template for the slim arms/"Alex" model.
An adaptation of the slimmer arms template, color-coded to match the appropriate faces of the skin: front, back, left, right, top and bottom. The checked areas represent the secondary layer.
Color-coded old skin template with all faces labeled.
Another skin guide, but on a black background. For the arm and leg sections only, "right" indicates those facing outward, and "left" indicates inward.
Deadmau5's skin[3] (not a guide). Notice the ears. See also: Easter eggs#Deadmau5's ears
Template for deadmau5's ears. Use other templates listed here for the skin.