Very easy project to play with leds and buzzer.  

You can turn on two leds throught 2 buttons.

If you press the first button the green led blinks and the buzzer beeps;

If you press the second button the red led blinks and the buzzer beeps like in the first case;

If you press all the buttons at the same time leds blink in a special way and the buzzer beeps twice ;)

 

It is an easy project and it is very costumizable, suitable for beginners.