I just pushed my second ever project to github (go gentle on me!):
roogle_graphics is a standalone Ruby module that generates simple
graphics using Google Chart API service. You place text and polygons
in a roogle_graphics plot, it emits a really odd URI that you post as an
HTML request, and voila, you get your png file to display.
You won't get fancy features, like choice of fonts or gradient-filled
polygons, but you DO get .png files without having to load a single
library or package. I've been using it and it serves my needs well.
See the README on github for more info.