I think you already know Adobe Photoshop:
Portable means that this is a smaller version, with the same features and everything, that is so small that can fit your USB stick.
Portable also means that all you have to do is to extract the folder, and NO INSTALLATION NEEDED! after you extract you can start using it. which means N0 KE! / @CT!V@T!ON 0R ^R@^K NEEDED! It Is So Simple!
Features:
Adobe Photoshop CS3 software accelerates your path from imagination to imagery. Ideal for photographers, graphic designers, and web designers, the professional standard delivers new features such as automatic layer alignment and blending that enable advanced compositing. Live filters boost the comprehensive, nondestructive editing toolset for increased flexibility. And a streamlined interface and new timesaving tools make your work flow faster.
Includes:
- New! Completely redesigned user interface.
- New! Fully customizable Windows & Shortcuts layouts.
- New! Smart filter.
- New! Auto Align & Auto Blend tool.
- New! Quick Select tool.
- New! Black & White Conversion control.

- Improved to camera raw.
- Improved cloning and healing.
- Improved curves controls.
- Improved printing controls.
- Improved bridge.

Download : 

http://rapidshare.com/files/101773895/PhotoshopCS3Portable.rar