Since GreasePencil has been merged into Blender 2.8, I've put a bunch of Rigged Dummies for Grease Pencil Workflow.
They are aimed to ease the drawing of characters by showing construction lines. It then become quite easy to draw complex perspectives and keep correct proportions.
This pack contains 3 rigs (Man, Kid and Anime Girl) with different shapes. More to come on the next releases (IK support, animal rigs,...).
Be aware that you'll need the last 2.8 version of blender (you can get it on buildbot).