I have just bought my machine and am still learning to use it.
I have been looking for free software solutions and have found a very useful set of plugins for google's sketchup.
search for PhlatScripT - The SketchUp CAM Solution
you may have to join the forum to see it or download but its well worth it.
you can easily draw in sketchup then get the platscript pluging to output the gcode.
the only thing is you need to change the file association from .cnc to .tap so that mach3 can read it.
you must set the parameters for your machine every time you open it because its set for the phlatprinter but that is easy to do.
there are lots of other plugins that work with the phlatscript that makes it very easy to get your ideas cut and for free!!!
http://www.phlatforum.com/ is the forum link.
would love to know if this helped anyone.