Graphics, art, image, and paint programs are so numerous it is almost irritating! Here are a few that really stand out.
GIMP is an advanced, pixel-based, image editing program. It can handle painting, photo retouching, batch processing, and even animation, with it’s use of a one-layer-per-frame scheme. With dozens of plug-ins and utilities, GIMP is the best choice for open-source image programs, giving commercial solutions a real challenge – and for free!
GIMPShop is a version of the GIMP designed to match the look and feel of Adobe Photoshop.
Inkscape is an open-source vector graphics program. Similar to Adobe Illustrator or Flash, Inkscape is designed around the SVG standard, but offers the same bezier-based vector editing you find in commercial packages.
Adobe offers the major commercial packages worth considering, such as Photoshop (for pixel-based editing), Illustrator (for vector graphics) and Flash (for vector-based animation).