AutoCad is the Industry standard and there are lots of add on packages. Prices start at about £600-00 (in the UK for the LT version)although I imagine buying direct from the States would prove much cheaper.
The package is versatile and probably does a lot more than most people could ever use. I used it first in the early '80s and used version 1.1, 1.2,1.3 etc. There were a dozen commands and we thought that it was the best thing since sliced bread. Now we are on version 2005.
The LT version is good enough for most mortals. The full version is about £3000.00
I use AutoCad but customise it for my own use. I don't use add ons, but plenty of manufacturers give away drawings etc which make life easier.
