Tactile Switch Buttons (6mm slim) x 20 pack
Available from April 20th 2014.
Slim clicky momentary switches are standard input "buttons" on electronic projects. These are half the width of classic 6mm tactile switches so they line up better on a breadboard, just plug them into every-other row. These work best in a PCB but can be used on a solderless breadboard.The two pins are normally open (disconnected) and when the button is pressed they are momentarily closed.
They also fit nice on the PiTFT.
They come in a pack of 20, they're pretty handy so you'll want to keep them around.