I assume what you're looking for is some type of Computer drafting/drawing program - I work with Autocadd and Microstation basicaly all day (when I'm not goofing off here!). These are fairly expensive (Thousands), powerful programs and require quite a learning curve - not what I assume you're looking for. Maybe take a wander through this link for starters:
http://www.broofus.com/construction/cad/index.htm
Also some of the freeware sites will have some drafting programs, but I believe you need to be cautious with what you might download at some of those - not sure what others on this site are using - it's not talked about that much.