At this time the more easy renderer is Podium http://www.suplugins.com/ free for image max 500*500 else 79$ for Student, 179$ normal
You select anything and just move 2 cursors :)
Can't be more simple!
But it's not now a "Stand Alone" so you must export in format 3Ds in the free Google Sketchup (the more easy (like Moi) and fun poly modeler) http://sketchup.google.com/
If you want fun try it :) (forms are moi of course :)