Hans Steiner, God of PD/USB and a darn nice guy, has released PDuino. In his words:

“Here’s the first test release of Pduino, a Pd firmware for Arduinoand a matching Pd object, . This allows you get data from the digital and analog inputs, and send data to the PWM and digital outputs. It also allows you to change the digital pins from input, output, or PWM. And you can choose how many analog inputs and turn on/off digital input.

“Keep in mind its a test release, the only thing I am not sure about right now is digitalInput, everything else seems to work fine. In the future, I’d like to figure out how to add the pulseIn feature.

“This firmware would work well with Processing, Max/MSP, Flash, whatever. Then the Arduino becomes a dead simple, cheap sensor box for the newbies, but still open for playing later.”