I needed lots and lots of switches, so i built this board to allow for 18 digital switches on each arduino analog input
basically, this is a version of the "multiple buttons on one analog pin" layout taken to an extreme. I used 1% tolerance resistors in the building to make my values more predictable across the several boards that i'm building. basically, the header with the square pad in "J1" is attached to an analog pin, the other header pin is attached to ground and 5v is applied to any of the pins in the center socket. I'm using 18 of 20 pins in a right angle socket and feeding 18 strand ribbon cable from all of my switches. I'm using 1/4" mono jacks as switches and shorting across them with a 1/4" plug that's been soldered across its internal contacts. the voltage is sent down the appropriate wire, through the number of resistors between it and the signal pin and a value is read by the arduino. each pin has more or less resistance between it and the analog in, so each one gives a different value.
I'll add some more photos and code soon as the project continues to develop.