3 Great Sources for Digital Art.

By nature, Gimp started out as a photo manipulation program, designed mostly to make tweaks to an existing photo.  As the community has grown, so have it's uses.  A lot of people use Gimp in combination with a Wacom Tablet to do some fantastic art.  Over time, I have stumbled on a few great resources for using Gimp to do digital art.  I hope these help you.
Check out these sources:
3 Tools Every Gimp User Should Know About
These 3 tools can really help you get the most out of Gimp.
Excellent list of digital art for absolute beginners.
This is an extensive list of tutorials that are directed toward absolute beginners in digital art using gimp.
Griatch's Art Tutorials
Griatch is a very talented Gimp user that is loved by the Gimp community.  His tutorials can show you some great methods that will make you a better gimp user.

Related posts:
Great Gimp Addon for Digital Painters - GPS

Make a Cool Wallpaper Using Gimp

This Gimp Video Tutorial will teach you how to make a cool wallpaper using gimp.  Here is the final image:

The cool thing about this tutorial is it focuses on using layer masks and layer modes to give you complete control, including the ability to change the color of the wallpaper quickly and easily.