Ball Bearings are very useful for things that must be supported and spin at the same time. This tutorial gives a how-to on making a ball bearing in Blender 2.6.
Step 1: First Circle
Blender is a free, powerful, 3D modeling program. If you have not already downloaded and installed it, do so.
Open blender and delete the default object. (Keep the camera and light if you want to render)
Click Add => Mesh => Circle. On the lower left panel you should see "Add Circle". Make this circle have 36 verticies and any radius.
Step 2: Basic Shape
Go into Edit Mode. Select all verticies.
1. E (extrude)
2. Z (target axis)
Type 0.3 (Extrude Z 0.3). Enter.
With only the top verticies selected, scale to 0.9. Extrude Z 0.3. Scale 1.12.
In the left panel with the entire model selected, click Recalculate Normals.
Step 3: Taking Shape
Now duplicate your work OUT of Edit Mode. Scale X and Y to 1.5. In Edit Mode on the outer ring, select the middle row of verticies and scale it to 1.2.
Step 4: Make It Solid
Add the Solidify Modifier of desired thickness to both objects in Object Mode. Now apply it.
On both rings, apply subdivide smooth 4 times (w=> subdivide smooth) in edit mode. Select the middle ring vertex layers and click smooth vertex until there is a pretty slope.
Step 5: Add the Slippers
To add the balls, just Add => Mesh => UV Sphere. Now duplicate and move until it is perfect.