Carl Dennis Buell is an amazing illustrator. He has worked for several decades with 'traditional' media but has been recently using Photoshop and a graphics tablet.
Check out
OlduvaiGeorge
A sample entry is here:
I�m A Professional, Don�t try this at Home:
I�m A Professional, Don�t try this at Home
Actually do try it! If you have any artistic talent at all, a Wacom Graphics Tablet and a layered art or retouching program like Photoshop can make you better quicker than drawing with pencil and paper.
It�s a matter of what you�re after, but I use Photoshop because I like the setup, I like the tool selection, and mostly because it�s what I had to learn on. The Wacom Graphics Tablet is an unbelievably wonderful bit of technology. The tablet is pressure-sensitive and the feel of the stylus on it is very much like the feel of a felt-pen on vellum.
I was worried at first, but it took me all of about 10 minutes to get used to drawing on the Tablet while looking at the computer screen. It�s so much a part of the way I work now; I actually have more problems looking at the paper when I use a pencil.
Carl then walks the reader through eleven stages of drawing a Mammoth starting here:

And ending with this:

Gorgeous work -- the blog has only been around since November 2005 but it will be added to the blogroll at the next update...