Google Sketchup is pretty amazing, for a free program. You can build up 3D models of things using primitive shapes, putting them together, zooming around and rotating, and even dimensioning. It’s tricky to use, but there is some valuable tutorial videos that explain things one tool at a time.
Here’s the workbench I’m planning on building:
I’m sure the free version has limitations (I must try printing, for example) but so far, it’s awesome.
Yes, it’s easy to use, and faster than 3ds max, more and more people start to use it.