Inkscape - Inkscape is a free, open source professional vector graphics editor for Windows, Mac OS X and Linux.
SVGO - Tool for optimizing SVG files
LaTeXDraw - LaTeXDraw is a graphical drawing editor for LaTeX.
SVGminify.com - Removes superfluous information reducing the size of SVG files
Ipe - Ipe is a drawing editor for creating figures in PDF or (encapsulated) Postscript format.
Scour - SVG Optimizer / Cleaner