As you can see in the previous post, I've been working on a project involving the kind of problems you might see on the SAT or GRE. I've been focusing on geometry to start with which means I have to create lots of geometric drawings.
I recently started using Inkscape and I would highly recommend it for the following reasons:
It's a free, open-source program;
It works with Scalable Vector Graphics (SVG). Scalability is a great feature;
Quick tip: you can draw circles and squares from a center point using the shift key.