Editors note:
This tutorial will not work in Adobe Photoshop CS and later versions.

Step 1 Create a new image and make a new layer.

Step 2 Click on the new layer and go to filter>render>3D Transform.

Step 3 You'll get a window to draw stuff in. Select the sphere tool and create 3 spheres. It may take some practice to get the hang of it. Use the black arrow (selection tool) to move an individual sphere and the white arrow (direct selection tool) to resize it. Try to get something like this:

Step 4 Now click on the trackball tool. With this tool selected, click on the image somewhere and drag. This will start rotating the spheres around. Move them around until the white part that was in back is completely in front, then press ok.

Step 5 You now have something that looks like a snowman on a new layer. You can go back into filter>render>3D transform and create a cylinder for a hat. You can also add facial features and a background. This tutorial was for the basics of the 3d Transform Tool, but feel free to use your imagination. Here's what I got: