RJ McNamara has been working on a very nice look quad motor holonomic drive platform. No videos yet but plenty of great pitcures (and CAD renders) of his setup.
He has three different versions, 2 with 4xPF motors and one with 4xNXT motors. The NXT one uses the Mindsensors Motor Multiplexer to control them all. He also has spaced 4 Ultrasonic sensors around, and checks the readings one at a time to minimise interference from the others.
At the end of each motor is 2 RotoCaster omnidrive wheels (That's right, 8 in total!)
Lots and lots of great pictures, as well as the full LDD cad designs for anyone who wants to download them.