Yet another good tutorial from Deviant Art. This portrait was done by Harbek. She provides some great tips for creating a portrait in Photoshop and you can clearly see the main stages of the painting. Note the way detail is applied to the image, with the brush size gradually going from large to small allowing for a much more realistic look.
A good tutorial shared by Aivre on Deviant Art. Aivre provides some good tips and concepts for getting started with photoshop as a digital painting tool, she also provides some good ideas about sketching in the program and how to establish some basic principles right in your sketch.
A good tutorial shared by Kayouvirus on Deviant Art. This is a good basic work flow to follow if you don't have one yet. Start with the lines, block in the colors, and move on to the depth work. A good visual demonstration.
An awesome tutorial by CharReed.com. This is an Art Rage tutorial, describing some of the features and uses of the tool. That being said all the principles can be applied to most other digital painting tools out there. A fantastic tutorial all in all.
A walkthrough graciously shared by Frost Concepts on Deviant Art. I really like this piece because it shows an interesting technique that can help create unique images. You can see it applied in the second step. A very clever way of creating detail.