I used a free package called Sweet Home 3D-it's available on Windows as well as Linux. And, like Kudzupatch said, gives you the ability to do a 3D "walk through" of the shop space-very handy feature.

It's easy to learn-my wife had been using it to design the rooms for our house and furniture layout. She recommended it to me when I planned my shop. You don't need drafting skills to use it-it's very intuitive.

You simply put "pieces of furniture" into the shop design and just re-name them as your equipment.
Here's the link- http://www.sweethome3d.com/

I tried to send a copy of a workshop plan using this package, but can't include a PDF to the Lumberjocks site.

But it turned out to be a very handy package to visualize machine placement, lighting fixtures, etc. so I'd recommend it to someone laying out their shop.

And for those guys planning a new shop- I can strongly recommend it as a very useful tool. My shop design process involve dozens of "versions" of the original plan-all easily modified and a PDF generated for my architect who was creating the blueprints for the building. As building costs rose quickly, it became easy to modify the layout, then get a cost estimate from the builder.
Gerry

 

If not already said,
when drawing the building and any "furniture" with doors, draw all the opening arc.
Draw also the extended drawers.
the same for any machine with substantial moving parts.