Gimp is the Supreme High Overlord of the imaging universe! Well, it's awfully good, at least. (A fork of it, Film Gimp, later renamed CinePaint, was used for a lot of hit movies). One of the plugins, gfig, that comes with Gimp allows you to do vector drawings.
"Sams Teach Yourself GIMP in 24 Hours" is online at
It was written in 1999 (I don't know if GIMP ran on MS Windows back then), but is still very helpful. From the book's intro:
"It has an unequivocally fantastic laundry list of features that tend to make even the most hardened hacker puzzle and delight at just how incredibly functional and polished GIMP really is. It is extremely utilitarian, fast, feature-laden, stable, expandable, and is possibly the greatest thing since sliced bread (and the Linux kernel). In short, prepare to be astounded and amazed!"
GIMP has improved a great deal since then.
More GIMP information: