I'm looking to use the arduino to play mp3 and wav files from the laptop.
I want to be able to press a manual switch which in turn sends a signal to the computer to play a particular small wav file. And I'd like to rig up perhaps ten or fifteen mechanical switches all operating different wav files.
This is for a theatre production.
Any help on this.
Paul
Write a sketch that read the digital ports in an endless loop and sends the results thorugh the serial interface to your computer.
If this is not enough of a hint: try some of the example sketches.
Udo
Here is a good and probably overall cheaper solution for you. This software is called Soundboard. It cost about $30 and allows you to assign individual sound files to a letter on your keyboard. Now this is a Mac only software solution but you may be able to find a similar option for a PC.
http://www.ambrosiasw.com/utilities/soundboard/
Just heard about it today on one of the many podcasts i listen too.
A board? I would expect to do this with free software. On the PC autoit AutoIt Scripting Language - AutoIt will do the trick. AHK will do it as well. If a keyboard does not look good enough the next step would be to rip a cheap keyboard apart and immediately get 100 keys or so. Cool idea digimike. Definitely better than to go for Arduino. Seems we are sometimes to focused on doing everything with out golden hammer 
Udo
I was thinking of AHK as well. It would be easy enough.