Following the trend of vector art programs, you may also enjoy DrawIt.
Demo for free (most features there), or ~$42 for the full thing. It’s mac only. I’ve used it. Inkscape does work on the mac, but it has to run under X11; yuck!
GIMP is good for raster (pixels), and it, too is free. Mac/Win.
You would also be surprised what you can accomplish with Open Office. This free office suite has all kinds of art/layout ability with a free office suite to boot! Mac/Win
Point is, if you are really trying not to spend much money, than you really don’t have to spend anything at all!