SketchUp is free from Google just Google it and download to your computer. You can
do just about anything with it, but it is especially good for conceptualization of
architectural design. The current version (November, 2010) is 8.0. These instructions
are based on this version. There is also a professional version, SketchUp Pro 8.0, that
they sell online for $495.00. Students can purchase a one year license of SketchUp Pro
for $49.00. But I would recommend downloading the free version from Google.