Inkscape. An Open Source vector graphics editor, with capabilities similar to Illustrator, CorelDraw, or Xara X, using the W3C standard Scalable Vector Graphics (SVG) file format.Inkscape supports many advanced SVG features (markers, clones, alpha blending, etc.) and great care is taken in designing a streamlined interface. It is very easy to edit nodes, perform complex path operations, trace bitmaps and much more. We also aim to maintain a thriving user and developer community by using open, community-oriented development. http://inkscape.org
GIMP is an acronym for GNU Image Manipulation Program. It is a freely distributed program for such tasks as photo retouching, image composition and image authoring. It has many capabilities. 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. GIMP is expandable and extensible. 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. http://www.gimp.org/
Blender is a free and open-source 3D computer graphics software product used for creating animated films, visual effects, interactive 3D applications or video games. Blender’s features include 3D modeling, UV unwrapping, texturing, rigging and skinning, fluid and smoke simulation, particle simulation, animating, rendering, video editing and compositing. http://www.blender.org/
MyPaint is a fast and easy open-source graphics application for digital painters. It lets you focus on the art instead of the program. You work on your canvas with minimum distractions, bringing up the interface only when you need it. MyPaint comes with a large brush collection including charcoal and ink to emulate real media, but the highly configurable brush engine allows you to experiment with your own brushes and with not-quite-natural painting. http://mypaint.intilinux.com/
The Alchemy drawing canvas has an intentionally reduced level of functionality. No undo, no selecting, and no editing. Interaction focuses instead on the output of a great number of good, bad, strange and beautiful shapes. http://al.chemy.org/
Krita is a KDE program for sketching and painting, offering an end–to–end solution for creating digital painting files from scratch by masters.
Fields of painting that Krita explicitly supports are concept art, creation of comics and textures for rendering. Modelled on existing real-world painting materials and workflows, Krita supports creative working by getting out of the way and with snappy response. http://krita.org/
Scribus is an Open Source program that brings professional page layout to Linux/UNIX, Mac OS X, OS/2 Warp 4/eComStation and Windows desktops with a combination of press-ready output and new approaches to page design. Underneath a modern and user-friendly interface, Scribus supports professional publishing features, such as color separations, CMYK and Spot Color support, ICC color management, and versatile PDF creation. http://scribus.net