Over time I've written and recorded a few tutorials, most of them for 3DTotal, ImagineFX and Gumroad. The following are some of the books and videos I threw my two cents in:

The Making of 'Gibbon Rock' - Gumroad

Beginner's Guide to Digital Painting in Photoshop: Characters - 3DTotal
Digital Painting Techniques: Volume 6 - 3DTotal
Digital Art Masters: Volume 9 - 3DTotal

Free Tutorials

The making of 'Serves Me Right' - Layerpaint

How to use occlusion shadows and master them - Creative Bloq
How to give your art a photoreal cinematic look - Creative Bloq

Portrait anatomy - Breakdown
Portrait study - Breakdown

Free Brushes

Thumbnail Brushes - Download