I use TurboCAD. It has been highly rated in several reviews of CAD
software in woodworking magazines over the years. Best thing is that
it is available free as TurboCAD LE Learning Edition at
http://www.al-ki.com/tcad/download.php.

As with most CAD programs, it takes some time and effort to learn. It
does nice drawings once you learn it.

Mr Fixit eh