I just posted part one of my three part series on layer blending modes in Photoshop. It covers some of the basics about the different modes, how to combine multiple images/textures into a shot, an alternate way of color and exposure correction, and a few other things.
The tutorials may seem a bit basic to the intermediate or advanced Photoshop user, but they sure would have helped me when I first started learning. Parts two and three are in the works now...