For starters, a free image editing program, Serif Photoplus. Appears to be a good alternative to Photoshop. Supports Photoshop-compatible plugins. They've got several other free programs.

Then, a free plugin to create panoramic images, PanoTools. Has versions for Windows and Mac. Windows version also has a plugin for GIMP.

Reptile is nominally a program to create "funky" tileable web backgrounds. Of course, "funky" textures can also be done. :-)

Microsoft-owned Creature House Expression is a free vector drawing program.

Finally, a free painting program, Dogwaffle. Download and enjoy.

-- erlik