If you are used with AutoCAD and for one or the other reason don't have AutoCAD, ProgeCAD 2008 Smart! might be an option. ProgeCAD 2008 Smart! is available for download at www.progesoft.com/smart. It can read and write DWG files compatible with AutoCAD 2007 and AutoCAD 2008. Personally I feel a bit uneasy about the concept of AutoCAD clones like this one but free is free.
Via ProgeSOFT blog