Inkscape

Jonathan Lapsley writes the following:

Inkscape is an Open Source vector graphics editor, with capabilities similar
to Adobe Illustrator, CorelDraw, using the W3C standard Scalable Vector
Graphics (SVG) file format.

It has an easy to use interface, with powerful tools.

It is very useful for editing files where you need to extract parts by
accessing the nodes.

It offers cross platform support.

The donation page is http://inkscape.org/donate.php?lang=en