Gimp offers you great image editing tactics that give you the feel of a high-end editor like Adobe Photoshop. It gives you layer control, floatable toolbars, and tons of tools for editing.

~Calamity

Note: The default download for this listing is an older version: 1.2. Along the right side, you can download a pre-release version that isn't released officially, but a quick sneak peak and what they've done so far.

For GIF support, download the GIF plug-in along the right side of this listing. UnZIP this and place the gif.exe in your Gimp plug-ins folder. Due to patent issues, Gimp is unable to supply this feature during the installation.