Blophome - Decorates, draws or designs any room in your house or office.
LibreCAD - An open source 2D CAD application for Windows, Apple and Linux.
Sweet Home 3D - Sweet Home 3D is a free interior design application that helps to draw the plan of house, arrange furniture on it and visit the results in 3D.
FreeCAD - An open-source parametric 3D modeler
Live Home 3D - Live Home 3D is home design software for floor plan creation and 3D visualization that suits both amateurs and professional designers.
SketchUp - 3D for Everyone