CharityBox is a project mainly written in ActionScript, it's free.
Load standardFirmata.pde on to Arduino Board - This can be found in Examples in the Arduino program.
This program has a button attached to digital input 2 on the arduino.
Check serproxy is configured to to the correct com port. - use /dev/cu- instead of /deb/tty-
http://code.google.com/p/tinkerit/wiki/TinkerProxy