Little clicky switches are standard input "buttons" on electronic projects. These work best in a PCB but can be used on a solderless breadboard. The pins are normally open (disconnected) and when the button is pressed they are momentarily closed.
Colorful Square Tactile Button Switch Assortment is bigger than the 6mm buttons and come in a pack of 15. Each button comes with a candy-colored square cap that snaps on. You get three of each color-- blue, grey, yellow, green, and red. The square plastic button tops affix easily to the tactile switch body.
The pack includes:
Ladyada’s Button Tutorial: www.ladyada.net/learn/arduino/lesson5.html
Adafruit Product Page: https://www.adafruit.com/products/ 1010