The first time I got in contact with Photoshop was when it was in version 3 and I've used it almost daily since then.
Photoshop is used for all kinds of retouche, composites, color-editing, 3d-textures and as a sketch-tool for building webpages.
Photoshop's companion for web-images. Certain webpage-layouts is easier to create with Imageready. Used for GIF-animations, button roll-overs etc.
When it comes to editing images for video/3D I use Cinepaint. Has good support for editing image-sequences and extreme color-depth.
A small but powerful program used for sketching, storyboards etc. Perfect complement for a Wacom-board.
Scanning is done in Silverfast Ai Studio. A very competent program that is updated frequently.

I have a few extra plugins installed for Photoshop but the most used are: