I've used Qcad and Pcad. Qcad I got about 12 years ago and it was like $30. I used it for designing the MarketMinder prototypes from start to finish. Pcad was free. Not sure if it's even still available. Linux comes with some CAD software that I've dinked with and seemed pretty decent. Haven't used CAD software in a while so can't remember any names offhand.