Blender is a powerful 3D program capable of modeling, animating, and game-building up there with the popular commercial programs. While versions up to the present 2.49 tend to be tough to learn, the upcoming 2.5 appears to have a redesigned user interface that might make it easier to figure out. Maybe.
Blender-oriented sites I've bookmarked:
Blender 3D: Noob to ProBlenderNationBlenderArt MagazineBlender Materials...And those are just a few offhand. I think you'll find BlenderNation most useful.
There are also a number of books available on how to use Blender. You should be able to find them in the computer manual section of your well-stocked book store.
Quoth Smelge:
Zbrush.
Basically, rather than building stuff out of base shapes and altering them, you have the digital equivalent of a lump of clay. You can mould and sculpt it how you want in 3d, and using graphics tablets. It's apparently easier to learn than most other programs.
Blender can do this too with its Sculpt Mode.
Quoth 26_994:
Well,I've heard about technology of auto-creating of "3D" with using existing "2D" .
There is also
Google SketchUp, a free, yet pretty good CADD-like graphics program that's easier to get started with than Blender is (there is also a pay-for Pro version). One of SketchUp's better points is its Photo Match ability, allowing a user to take a photo and sketch over it, using perspective to create a 3D model.