Inkscape - Inkscape is a free, open source professional vector graphics editor for Windows, Mac OS X and Linux.
Inkpad - Inkpad - Vector illustration app for the iPad.
SVGO - Tool for optimizing SVG files
Adobe Illustrator - Adobe Illustrator is a vector graphics editor.
SVGminify.com - Removes superfluous information reducing the size of SVG files
Scour - SVG Optimizer / Cleaner