My first article for Ghacks is online and is called "Do your own awesome vector posters with Inkscape & potrace":
This article will cover a very powerful but little advertised feature of Inkscape. If you don’t know it, Inkscape is a free vector graphics editor, counterpart of Adobe Illustrator (like GIMP is Photoshop’s counterpart for raster graphics).Read it on Ghacks.
This feature is Inkscape’s vectorization tool, made possible by the integration of potrace.