The ball is from an old computer mouse, with the rubber coating removed (you could use a marble as well). A crafty person should never throw perfectly good stuff in the trash. Just hang onto it, and eventually you'll find a new use for it down the road!
With some parental help, this can be a kid-friendly project. Building a solid table with a functioning paddle assembly requires some basic woodworking skills, and may be fairly difficult without proper guidance and appropriate tools. But once the paddle assemblies are in place, just about anyone can build ramps and jumps or anything else they can imagine for the upper part of the table. To me that's where the real fun lies--creating various obstacles and then seeing a ball bounce around all over and through them, somewhat under your power.
This is a great project for parents and kids to take on together!
Please check out the video at the end of the instructable to see it in action.
Step 1: Table top
This should be a helpful guide though, to show you how it can be done.
The table top is a piece of melamine which used to be part of a large router table top. It had numerous screw holes in it that I filled with putty. The dimensions are 36" by 20", not including the sides. The sides are 3/4" plywood that was ripped into 2 1/2-inch wide pieces.
The sides are attached to the piece of melamine with screws. To get a precise fit, it is very useful to use clamps to position the sides to the melamine, and then drill pilot holes into which you drive your screws.
A piece of two by four was screwed to the back to give the table its tilt.