CG Boost - Zach Reinhardt and his amazing team are making top quality courses over at CG Boost. This should be your first stop for learning Blender.
Vaughan Ling - Heavypoly - Vaughan Ling is an amazing concept artist, illustrator and 3D modeler. He even made his own scripts for Blender to make it easier to use.
Jama Jurabaev - Concept artist for movies and TV and advocate of Blender for concept art.
Jan Urschel - Another movie concept artist and advocate of Blender.