Inkscape - Inkscape is a free, open source professional vector graphics editor for Windows, Mac OS X and Linux.
Epic Pen - A windows tool for drawing over your desktop and applications
SVGO - Tool for optimizing SVG files
Gromit-MPX - Create annotations by directly drawing on your screen.
SVGminify.com - Removes superfluous information reducing the size of SVG files
Ardesia - Ardesia is an usefull software for use your desktop as a Sketchpad.