Hi, we thought that this may be of interested to some of you.
We just started a kickstarter for VoxCube, an 8x8x8 RGB LED cube which is compatible with Raspberry Pi and Arduino. In fact, it has an ATmega1284p onboard which could be program directly to drive the LEDs, no external microcontroller needed.
The Cubes are also chainable to be able to create large displays. The image below is four cubes chained together.
A single cube;
Here is a snippet of the PCB where we have mounted the ATmega1284p;
You can check it out here https://www.kickstarter.com/projects/2135028730/voxcube-8x8x8-rgb-led-chainable-cubes