Photoshop

Adobe Photoshop is very likely the most known image editing software. It is an industry standard application, it belongs to the suite of Adobe applications, and it comes with Adobe Image Ready, which was especially designed for the needs of designing webpages. Very many different groups like graphic designers, web designers, video producers, press editors, photographers, etc. use Adobe Photoshop and it is very likely the most powerful tool image software. There are already many versions of Photoshop, the latest is Adobe Photoshop CS3. You can also comfortably work also on older versions, basically since Photoshop has layers, the versions did not differ too much.

=Tutorials= You can can find many tutorials online, some start at the beginning, some are advanced.

Basics

 * Sketchpad.net offers a very good tutorial right from the basics, every step is well shown and supported with video showcases.
 * SoftwareTrainingTutorials.com also work on the basics.
 * PhotoshopEssentials.com is also a very rich source for Photoshop tutorials

Advanced
If you are familiar with the Photoshop basics you are maybe looking for more fancy design.


 * www.absolutecross.com has very beautiful design tutorials.
 * Psdtuts.com shows advanced design in Photoshop.
 * PhotoshopCafe.com is another website dedicated to Photoshop.

What's new
With every new version Photoshop offers some new astonishing features. If you want to keep pace:
 * PhotoshopCafe.com about what is new in CS3.
 * about.com also has an article on CS3.