Light: A very detailed article, in several sections.
Part 1: The basics
Part 2: Light direction
Part 3: Natural Light
Part 4: Artificial and indoor light
These articles are the basis of a new book which I am in the process of writing, it is due for release in spring 2009, watch this site for updates. The book will be a comprehensive guide to lighting for artists, and will go into much greater detail.
Digital inking: How to ink digitally and get good results
Good Wacom technique: How to avoid the shakes when drawing with the tablet
One point perspective trick: How I did the floorboards in Rufus and Rex
Three point perspective trick: Block models as a drawing aid
Lighting in passes: A 3D technique applied to 2D.
The Monster Makeover: A Photoshop painting tutorial, featuring overlay layers