Vector Magic - Easily convert JPG, PNG, BMP, GIF bitmap images to SVG, EPS, PDF, AI, DXF vector images with real full-color tracing, online or using the desktop app!
Krita - Krita is a professional FREE and open source painting program. It is made by artists that want to seaffordable art tools for everyone. Concept art. texture and matte painters, illustrations and comics.
Inkscape - Inkscape is a free, open source professional vector graphics editor for Windows, Mac OS X and Linux.
Autodesk SketchBook - SketchBook drawing and painting software provides designers, architects, and concept artists the tools to sketch ideas quickly and create beautiful illustrations.
Sketch - Professional digital design for Mac.
Clip Studio Paint - The artist's software for drawing and painting.