Adobe Photoshop is a commercial bitmap and image manipulational program developed and published by Adobe Systems. It is the current and primary market leader in this field. Though it is the best, it is also one of the most expensive programs to buy. Luckily, there are quite a few free alternatives to Photoshop.
1.GIMP
GIMP is a freely distributed program for such tasks as photo retouching, image composition and image authoring.It can be used as a simple paint program, an expert quality photo retouching program, an online batch processing system, a mass production image renderer, an image format converter, etc.It is designed to be augmented with plug-ins and extensions to do just about anything. The advanced scripting interface allows everything from the simplest task to the most complex image manipulation procedures to be easily scripted.GIMP is written and developed under X11 on UNIX platforms. But basically the same code also runs on MS Windows and Mac OS X.
Paint.NET is free image and photo editing software for computers 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.
3.GIMPshop
GIMPshop is a modification of the free/open source GNU Image Manipulation Program (GIMP), intended to replicate the feel of Adobe Photoshop. Its primary purpose is to make users of Photoshop feel comfortable using GIMP.
Artweaver lets you paint creatively with the help of a huge range of painting tools. You can create sketches from photos or just experiment with colors.Artweaver is available in two versions. A Artweaver Free version for free and a Artweaver Plus version with costs which has more features than the free version
Hornil Stylepix is a free graphics editing program. It’s light and powerful photo and image editor with professional tools for mid-range of users.
An image editor that provides powerful tools for designers and photographers alike.It doesn’t require a gig of RAM or half of your hard drive for swap space, but that doesn’t mean it skimps on the features.
Nice and great info