http://toshicg.gumroad.com/l/skeleton_rigify

In this step-by-step video course, you'll learn how to rig a Skeleton 3d model. We'll be using Blender - the free and open-source 3d content creation suite - and the free auto-rigging system Rigify.  THE FINAL RESULT FROM THE COURSE  By the end of the course, you'll have a fully rigged skeleton model, animated using mocap and retargeting. You can even get it ready for export to a game engine, should you wish to.  WHY RIGGING A SKELETON IS DIFFICULT  The rigging and weight painting techniques you learn in most tutorials are meant for "standard" characters with skin and clothing. Rigify offers amazing features such as twist bones (aided by bendy bones) out of the box. Automatic Weights and advanced add-ons such as Voxel Heat Skinning help us quickly skin connected meshes.