The X-CAD Web site says it's free for 30 days to 100,000 users.
X-CAD, a parametric 3D design program, is available at no cost to 100,000 who register by August 1 at x-CAD.net. In addition to letting users create 3D mechanical designs equal to well-known midrange solid-modeling brands, X-CAD has an easy-to-use Windows interface, integrated Help menus and tutorials, and real-time collaboration with other users wherever they are located. It's a free download after registering the person's e-mail address on the x-cad.net Web site. The software is not a demo or trial software, say developers. X-CAD provides fully functional, intelligent, parametric sketching with an array of features such as "on-the-fly" automatic constraint capture, autodimensioning, various sketch tools including lines, circles, arcs, polygons, and splines, and a complete set of constraints such as vertical/horizontal, perpendicular, parallel, tangent and more.