I really kick myself now for not including a mention of gnuplot in “Painting the Web”. I had one chapter on graphics and data, and it would have been a nice fit. However, it does need a nice installation environment for the Mac, and that was one of the criteria for including mention of tools.
We’re told that a Mac-specific installation of gnuplot is coming. When it does, I’ll include a link in the graphics tools section of the book’s supplementary site.
Another handy graphical tool is svgfig, which allows you to draw mathematical figures in SVG using Python. This tool should be very simple to install if you have Python installed. Using it, though, does require an understanding of math. Of course.
I would say that 2008 is the year of SVG in addition to the year of semantics. Works for me, though perhaps I should have called my book, “Painting the Semantic Web”.
(Thanks to Michael Bernstein for mention of svgfig)