Photoshop

http://photoshopcafe.com

If you want to learn about all kinds of programs, Photoshop Cafe can be your best choice.
Here you will find tutorials for Photoshop, Lightroom, as well as a number of other popular photo editors.

http://filtergrade.com

Quite a neat site that provides photographers with Photoshop and other post-processing tools.
There is also a lot of interesting tutorials, free downloads and simple tips for editing photos on your blog.

http://photodoto.com

Another great site to learn how to edit photos.
There are no long teachings. Nothing superfluous in the tutorials on various photo editing techniques for Photoshop, Lightroom, and other photo editors.

http://photoshoptutorials.ws

A good place to learn something about editing photos. Photoshop lessons, a wide range of tips, tricks and free downloads are all related to the art of post-processing.