What programming language do we use? [Nov. 12, 2011, 8:27 p.m.]
Projects in this class should be in Processing. You can run a Processing program (called a sketch) on a computer and have it interact with the Arduino board over a USB cable. You can download the free Processing software from http://processing.org/download/ and prepare your Arduino by following the directions on this page: http://www.arduino.cc/playground/Interfacing/Processing
Programs for the Arduino are typically in the C programming language. You can download the free programming software directly from http://arduino.cc This is especially true when the Arduino is disconnected from a computer.