This guy's stuff is AMAZINGLY detailed and just wonderful to look at. He is also highlighting and decribing different tools and techniques he is using or learning about. It really is an interesting blog/project to follow.
Also wanted to plug another site out there on the inter-web. idrawdigital provides web resources, tutorials, etc... all relating to illustration (particularly digital illustration, inking, colouring, etc..). This is actually where I found out about the above mentioned blog. I have already found some valuable resources for Photoshop and Illustrator on this site. Check it out if you are interested in advancing your digital art tool box.
More to come, probably once book 5 is complete. Give me a week.