This is a cool piece of software, well worth the price (free):
http://sketchup.google.com/
It only took me a couple hours to figure it out. It's not perfect, it's a little quirky, but it really makes it easy to visualize a project. I already caught a few design flaws with my 2D sketches thanks to this program.
Here's a shot of my new design:
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New Jersey Marijuana Dispensaries