My latest personal project, pygpibtoolkit, holds a simple HPGL plotter trying to emulate the HP7470A GPIB plotter, using the very nice and cheap Prologix USB-GPIB dongle. This tool is (for now) called qgpibplotter (since it is using the Qt4 toolkit).
Tonight, I took (at last) the time to make it work nicely. Well, nicely with the only device I own which is capable of plotting on the GPIB bus, my HP3562A DSA.
Now, you just have to press the "Plot" button of your test equipment, and bingo! you can see the plot on your computer.