At the moment dealextreme dot com is selling 32 x 8 matrix clocks for about 10 euro each.
Registers are from left/top 0 to right/bottom 63, 4 bits. Atmega8L on an internal 1 Mhz clock. Connector for a ISP programmer. But watch out, 5 volts power supply.
And if you want to see some action, here falling digits