Inkscape is vector graphics software for creating icons, illustrations, logos, diagrams, maps and web graphics. It's cross-platform, extremely feature-rich yet simple to use, and extendable. Users therefore include design professionals as well as hobbyists. It's engineered around the open and standard SVG (Scalable Vector Graphics) format. Its sophisticated drawing tools easily match up to Adobe Illustrator, CorelDRAW and Xara Xtreme. Inkscape also can import and export to AI, Encapsulated/Posts
GIMP is a very versatile graphics editing software. It works on bitmap images, provides layered editing, a plethora of drawing and colorization tools, photo enhancing and retouching features and filters, programmatic effects, various extension and scripting capabilities, and itself provides a highly adaptable multi-window interface. It can open nearly any graphics format, or import Photoshop, PDF, Postscript, SVG and other vector formats even.