I recently became aware of Robert Thomas and his work with photography. He has a fantastic site that contains many different Photoshop and photography tutorials. Mr. Thomas believes in sharing knowledge with others, which is a vital component in education.
To view the Photoshop and photography tutorials, please click on the link to visit Photo Blog Stop.
Because of his background, Mr. Thomas is able to explain coherently why and how certain tools in Photoshop work, and how different tools and processes interact with each other. By way of example, I read an article over at PetaPixel by Michael Zhang that discussed a Robert Thomas tutorial that explains how Photoshop blend modes work. It is interesting and fun to learn more about how to work effectively at processing digital images.