DoubleCAD XT Pro makes one of the best free 2D CAD software available for the Microsoft Windows Operating System. The pro version of DoubleCAD now features Ruby scripting. There is a video on the Ruby scripting available in the pro version of DoubleCAD. There is a web page about the ruby scripting at the DoubleCAD web site.
The suggested price of DoubleCAD XT Pro is around $700.00. That is a little pricey. You can get an IntelliCAD program with embedded AutoLISP for about half that price. Still, with Ruby scripting, DoubleCAD XT Pro is probably still a better deal than AutoCAD LT, which doesn’t have the ability to run AutoLISP code.
If your looking for an AutoCAD alternative, I strongly recommend BricsCAD, which even runs on Linux!
The Sunburned Surveyor