Here’s an excellent (and very popular) tutorial on creating high dynamic range (HDR) images; the author focuses on realism instead of going overboard with the application of HDR.
In this Photoshop tutorial, you’ll see another method of correcting colors by using the levels-adjustment feature and by sampling colors with the eyedropper tool.
This Photoshop tutorial shares a more complex method for sharpening photos using a variety of techniques such as using filters and setting threshold adjustments.
Learn the basics of coloring techniques via a practical example (coloring the hair of a black-and-white photograph) in this wonderful Photoshop tutorial.
Cluttered backgrounds can be a distraction from the photo’s subject. Here’s an introductory-level tutorial on reducing visual clutter in the background of a photograph.