Elco Jabobs wrote a modified copy of his ShiftPWM library for driving a LED matrix.
I made a little test board to give it a try. His library works well. In theory, it only needs inexpensive shift registers to drive a RGB LED Matrix. In practice, a LOT of transistors and passive parts needed to be soldered.
I only made 3 of these boards. 2 were sent to Elco Jacobs and "ematson" who contributed to the effort on the Arduino forum.