CG Training From Neil Blevins
San Francisco Artist Neil Blevins has a great CG Education page. There you will find dozens of posts full of technical, design, and artistic knowledge. His Lighting, Materials, and Art Theory categories are a must read. And, even though many of his tutorials are based on 3ds Max, most concepts can be applied to any 3D package including Cinema 4D.
Hat Tip to Colin Evoy Sebestyen