Posted by Colin

Inkscape

It runs on all operating systems, "Inkscape is an open-source vector graphics editor similar to Adobe Illustrator, Corel Draw, Freehand, or Xara X. What sets Inkscape apart is its use of Scalable Vector Graphics (SVG), an open XML-based W3C standard, as the native format."

Has always been one of my favorite graphics programs, basically Paint on steroids. May not be cool/helpful for everyone but I know this community is filled with artists who might enjoy this.

https://inkscape.global.ssl.fastly.net/media/resources/file/inkscape-0.48-ferrari.png (Unsupported image host)

More examples of projects done on Inkscape