Just downloaded Double-CAD-XT. Pretty powerful for the price (exactly $0.00).
http://www.doublecad.com/Products/DoubleCADXT/tabid/1100/Default.aspx
Apparently, Part of the AutoCAD/TurboCAD family (IMSI). Seems to import a lot of older drawing formats quite accurately, and I can use older symbol libraries (including those I have created myself...)
Apparently, only available in Windows versions- I haven't tried it yet with Wine or VirtualBox.