Can anyone tell me if it is easy to configure Quartz Composer to take serial commands like .....Serial.print("A"); from Arduino? I want to trigger a movie from Arduino and it seems it is a possibility! Thanks for any help
You should try GoBetwino.
It is made for doing stuff like that + a million other things.
Awesome but i need to use Mac i'm afraid 
QC has handlers for MIDI, so if you have a MIDI interface you can use the MIDI Library to do it.
But, this sounds more like a job for Applescript.
Search for SerialPortX or AppleScript Proxy... either one should do the job.
You can also get into quartz composer using OSC so you need to run Ardunome Serial to do that.
Alternately there is a free third party serial port patch available from Kineme:-
http://kineme.net/QuartzComposerPatches
This is looking good guys!!! Thank you very much!!!!