Here you will find a growing number of examples and tutorials for accomplishing specific tasks or interfacing to other hardware and software with Arduino. For instructions on getting the board and environment up and running, see the Arduino guide.
Knight Rider example
Read a Pushbutton
Read a Tilt Sensor
Read a Potentiometer
Read a Resistive Sensor?
Read a Piezo Sensor
3 LED cross-fades with a potentiometer
3 LED color mixer with 3 potentiometers