Adobe Home of Photoshop. Some tips at their website.
Alchemy Mindworks Inc Makers of Graphic Workshop (viewer, slideshow and multiple format file conversion) and Gif Construction Set for animated graphics (GIF). Free try-out.
Alien Skin Software Maker of filter plugin collections Black Box and Eye Candy.
Andy´s Art Attack! Tips, graphic info and files, links.
Metatools Maker of Kai's Power Tools, KPT Convolver and Bryce 2. Check out Kai's Power Tips and Tricks for Photoshop!
POV-Ray Freeware, powerful raytracer. Have a look at the Raytracing Hall of Fame!