64Buttonmatrix
From the MAKE: Flickr pool

Spikenzie Labs’ impressive Button64 project offers a whole lotta input for Arduino/etc –

Decoding a button press is done with the help of a MCP23S17 port expander from Microchip. This chip has 16 general purpose I/O pins (GPIOs). Eight I/Os are used for the columns and other eight for the rows, forming a 64 button matrix. The columns (port B of the MCP23S17) are set-up as outputs and the rows (port A) inputs.

One of the great features of this project is that there are no diodes! Unlike many button matrices, it’s just the buttons and the MCP23S17.

Great aesthetics for such a useful device. It’d likely be a great interface for Arduino-Bingo ;)
Thoroughly detailed description of how it all come together in software/hardware over there – Project 64 / 64 Buttons

More:

1.5 hours of wiring …

Makershedsmall
Mksp4-2
Arduino Duemilanove