Tinkerlog presents a 64 LED matrix howto, controlled by Tiny2313 and powered by only 2 AA batteries. Check out the following demo video:
64pixels from tinkerlog on Vimeo.
I really love the simplicity of this project. The ATtiny2313 is a good fit on the back of the 8x8 Led matrix, though not placing resistors in between the LED and IO are a bit risky. But using 2 AA batteries, roughly 3V input and 20mA max output from 2313 should not burn the LED out:)
The source code is also ready on the tinkerblog website, so follow the steps there and build it in the weekend! Have fun!