FreeCAD -

A9CAD was specially developed as a useful, powerful and user-friendly two-dimensional 2D CAD application. A9CAD is a handy CAD software that allows you to draw shapes, perform drawing changes, and modify entity attributes via properties window. It supports industry standard DWG/DXF drawing formats.

DoubleCAD™ XT is an AutoCAD LT® work-alike. But free. Frankly - the way of work is a bit different, but If you are an AutoCAD LT® user, DoubleCAD XT will immediately feel familiar.  Familiar menu, menu items, tools, icons, command line, keystrokes... and a familiar intelligent cursor. Even if It's native file format is different - AutoCAD® drawings opens, displays and saves reliably. It uses AutoCAD fonts SHX. But you will miss AutoCAD® linetypes (*.LIN) and also hatch (*.pat). DoubleCAD includes relatively enough chatch patterns, but situation with linetypes is a bit worse. As a big disadvantage we see impossibility of any extending via LISP or via other developing method (perhaps over time it could be changed).

With FelixCAD LT, where nearly 300 Powerful 2D drawing and editing commands can be used to create professional quality designs from scratch. You can select one of two optional interfaces - AutoCAD or PowerCAD. FelixCAD LT supports fonts *.SHX, line types *.LIN, hatch patterns *.PAT First month you can use it for free - after first month you have to register. FREE For The First 1 Million Users!

HYCAD is a useful and general purpose CAD program, green and small but powerful. It can export multiple format files,such as BMP JPG PNG DXF XMG WMF EMF DWG EPS SLD CGM SVG PDF etc. it is easy to learn and use and much like AutoCAD®.