Pinta is a lightweight photoshop-style drawing and editing program.  Not quite as complex and feature packed as Krita or Photoshop, yet still includes a wide variety of familiar features including, layers, adjustments, effects, clone-stamping, gradients, text and more. Users of Photoshop will feel at home with a similar tool layout and workspace.

Finally a Photoshop alternative that is better than GIMP!  Krita is an Open Source FREE software with many advanced features.  Features of Krita that make it one of the best alternatives to photoshop include:

Layer Styles (Drop Shadow, Bevel, Glow etc.) YES!
Touch-friendly input for painting on tablets and touch enabled screens
Brushes (Import and create)
Import AND Save Adobe Photoshop files! (.PSD)
Vector layers, Text Layers, Vector Selection
Free scaling/transform selection & layers
Group Layers
Layer Masks
Save TIFF, PNG, JPG, and more popular graphics file-formats
CMYK Support
Adjustments (Color Balance, HSV, Levels)
Filters and Effects

Krita has many more features, and it's user interface is close enough that Photoshop users should feel fairly comfortable getting around and figuring out the differences here and there.  This is an amazing find for those looking for a powerful alternative for Photoshop.  Though it was originally designed for digital painting, it has become quite a robust piece of graphics software, and best of all, it's FREE!

Versions for Windows (32bit/64bit), Mac OSX, and Linux are available for download on the website.


https://krita.org/download/krita-desktop/

Paint.net is a photo and graphics editing tool that has much of the same main functionality, tools, and effects that Adobe Photoshop has.  The program is fast, and quite stable.  With plugins available and support for brushes, layers, and more, this FREE software is a great alternative to Photoshop for those wanting Photoshop-style editing ability without the price-tag.
More from the GetPaint.net website:
Paint.NET is free image and photo editing software for PCs that run Windows. It features an intuitive and innovative user interface with support for layers, unlimited undo, special effects, and a wide variety of useful and powerful tools. An active and growing online community provides friendly help, tutorials, and plugins. It started development as an undergraduate college senior design project mentored by Microsoft, and is currently being maintained by some of the alumni that originally worked on it. Originally intended as a free replacement for the Microsoft Paint software that comes with Windows, it has grown into a powerful yet simple image and photo editor tool. It has been compared to other digital photo editing software packages such as Adobe® Photoshop®, Corel® Paint Shop Pro®, Microsoft Photo Editor, and The GIMP.

Pixlr.com is a great online alternative to Photoshop.  Nothing to download or install. It all lives on the web and is accessed through your flash-enabled web browser!  If you are used to how Adobe Photoshop functions, you will be at home with the advanced Pixlr editor.  It looks amazingly a lot like photoshop, and even many of the menu structures and options are set up the same.  Complete with layer effects, masks, and more, if you need a FREE Photoshop alternative, give Pixlr.com a try!