LibreCAD - An open source 2D CAD application for Windows, Apple and Linux.
TigerCad - A completely free, simple technical drawing software (CAD)
QCAD - QCAD is an application for computer aided drafting in 2D.
A9CAD - 2-dimensional CAD program supports industry standard DWG/DXF drawing formats
TYCAD - TYCAD is a application for computer aided drafting (CAD) in two dimensions (2D).
JustCAD - JustCad is designed, to make cad drawing as simple as possible.