For all your home/office modeling needs, Project Dragonfly from Autodesk does the job easily. It is a free floor-plan design web-based tool for do-it-yourselfers. Once the 2-D plan is ready, it can be viewed in 3-D, and also emailed to friends & family. See an introduction video here. A review is available here.
Screenshot: Project Dragonfly
Software for modeling your home