Just a .02 to add re: the CAD discussion...
Someone mentioned AutoCAD and Microstation, but I'd also like to throw Vectorworks out there. If you are interested in CAD, and are looking at a more designerly approach, then Vectorworks might be worth looking into (I'm a theatrical designer, and there is a lot of debate in our field between AutoCAD and Vectorworks - mainly between the scenic and lighting design communities).
For my money, Vectorworks is a good CAD program that has a simple Vector interface. If you can use Illustrator and Photoshop, then, with a small amount of a learning process, you can at least get started in VW.
Admittedly, it is more "designer" friendly, and less of an engineering tool, which is why I think it is popular in the theatrical and Interior Design worlds, and less so in any of the various engineering worlds (although you can purchase engineering and landscaping packages for it, so perhaps I'm mistaken).
As an example of a VW drawing: while I mostly use PS, my two ships for Serenity primarily done in Vectorworks. Small bits of post in PS.
Two ships for Serenity
Just trying to throw other options out there...