I just wanted to throw some helpful things around.
- Enliighten - Absolutely amazing artist with some excellent instructional media.
- Daarken's Photoshop Brushes - I use a few of these religiously. They are excellent as far as texture and versatility are concerned.
- Essential Illustration Brushes Version 3 - Absolutely great as bases if you want to get better at editing brush settings. A lot of these are just the basic stuff, but this is a great all-around set if you're looking for a solid brush set.
- Etoli's Photoshop Digital Painting Tutorial - Pretty old, but still full of some solid stuff. I particularly like this for the fact that it features instruction on removing traditional lines from a background!
- Slater Bird Wing Collection - Thousands of images of the wings and tails of birds via the Slater Museum of Natural History. Really great images here and an awesome place to study bird wings.
- Peter Dinklage Portrait Process - A very unique and stunning digital technique worth taking a look at.