now if you don't have it already on your pi: install python
sudo apt-get update
sudo apt-get install python-dev
sudo apt-get install python-rpi.gpio
you need the gpio thingy to controll your pi with buttons and let some leds light up
And you'll need some soldering...
I've added 5 LEDs and 5 Buttons and three switches (of which only one is connected to the pi)
and here's my wiring diagram :D
You'll need some resistors for the red, green and yellow LEDs and some pullup resistors for the buttons (not sure if they are called pull down resistors in my case as they connect the pins so ground while the button is open...).... pull down.... pull down resistors!