Art of Illusion, a free, Java-based, open-source 3D graphics suite from Peter Eastman, is powerful and flexible enough for pro users, but its ample explanations, tutorials, wizards, and other assistance actually make it possible for beginners to learn the basics of 3D modeling just by using it.
Art of Illusion's user interface is based on Java Swing, so it's almost completely customizable. The default layout consists of four view windows displaying selectable front, back, and side views as well as a camera perspective; a sidebar containing the Objects List and Objects Property Panel; and a set of tool icons that you use to create, render, manipulate, and refine objects, lines, surfaces, and shading. File menus entitled Scene, Object, and Animation access a variety of controls for each main function; for instance, clicking most entries on the Object menu calls up a variety of properties dialogs for setting everything from surface texture to the angle, intensity, and color of the light illuminating the object. This software offers one of the best and most comprehensive selections of help we've ever seen, beginning with a classic tutorial on creating an hourglass but also showing up in thoughtful touches, such as the way the What's This? contextual help shows detailed explanations and the full Help menu index when you hover the cursor over an item, instead just a word or two. The icon toolbar has a familiar feel, although the controls are unique. Art of Illusion is actually quite easy to use, though we can see it would take a lot of practice to master. In essence, what you do is create 3D "objects"--a boy and his dog, for example--and background "scenes" for them out of basic geometric shapes, much like building blocks, and gradually smooth and refine them into a finished image. It takes a bit of practice, but it's actually a lot of fun; many hours could fly by with this program open.
Art of Illusion is capable of producing sophisticated 3D images and animations, accurately rendered and useful in a wide range of applications and media. It can be expanded, refined, updated, and customized, and it offers top-level assistance, including a forum. Incredibly, it's also completely free.