With my desire to have an array of connectors, here is another one that is the mate to the disc ball joint: http://www.thingiverse.com/thing:5126

This thing has the balls attached to the disc, and allows clamps to attach to those balls,and move freely around. It is parametric, so you can add as many balls as you want (increase the disc size as well). Then you can attach things like the included sphere clamp.

By default, this thing creates a 10mm radius ball, which fits nicely with the rest of the Yazzo ball caps.

It is a very challenging print, depending on your printer. The primary challenge is in the overhang created by the balls lifting the disc off the X-Y plane. You could probably print it from its edge, and it would not require as much support structure. It just depends on your printer.

In the pictures, the color is NOT paint. I used color filament from MakerGear. The Yellow/Blue is fairly striking I think.

UPDATE: 16 Dec 2010
Increased the grabber's enclosure because it was too weak to grab

1) Figure out your design, that needs this type of joint
2) Print a few of them out
3) Attach your various clamps (the disc joint will fit
4) Rejoice!