Did it this month.
Using the Arduino Uno R3 to illuminate a 5x5 flat led table. Just one short example of the multiple possibilities of this hardware.
Same system used with the 3x3x3 cub but in flat.
Not 27 leds but 25, the rest is the same.
Material used:
25 Leds in 5x5 flat.
12 Resistors
3 Transistors NPN
a lot of cable...

1st transistor to 9 leds
2nd transistor to 8 leds
3rd transistor to 8 leds