I just finished wiring this madly wicked project up, and I am so grateful to finally having it spit audio out of my speakers!
To sum the process up:
I wired the red (5v+) and black GND power cables up to my arduino uno and grounded pins 14 and 10.
(used the arduino for pin 18 and 20 - direction and stepping pulse)
I managed to solder some wires onto the W/R heads (checked for the GND line with my multimeter - one didn't have any resistance so I figured that'd be the one).
The input was gained through a behringer mixer and the output was hooked up to the tape heads of and old Fisher Price tape recorder. :)
I then tried to accomplish the following: adding my own pulse to the spindle motor as this guy did:
http://www.instructables.com/id/floppy- ... d-control/
I then ended up with somehow screwing up the motor and now it is jammed and just sends out clicks when trying to rotate. I doesn't matter that much as I already have another drive ready for hacking.
This time I will build it into a casing and have switches for the different controls as direction and record/play, LED's for indicating write protect, track 0 and disk presence.
But I would like to find out how to adjust the spindle motor speed before throwing myself into the hellfire of soldering and wiring once more.
I tried soldering a wire to one of the pins going to the spindle motor circuit board, on the pin that got the motor running when grounded. But it wasn't the right one. The Floppy Drawbot Dude said he measured a 1 MHZ pulse on pin 5, which he cut the connection to and added his own pulse. Sounds über-neat and that's definately where I'm going!
Imagine being able to slow down the RPM of the motor and playing your audio in different pitch. The guide on instructables said it was possible to slow it down to 120 rpm before it was loosing motion, that's over half the speed of the playback! I wonder how fast it can run and still play the audio! I am so excited to do this! Hope somebody is willing to take this challenge up and test it out! (I've heard that a 5.25" drive typically has a built-in speed control knob!)
Oh, and here's some footage of the drive when it was just done - and still alive. (Notice the mess in my hut!)

YOUTUBE LINK HERE
Update:
I now managed to adjust the motor speed by following the guide i provided at page 1 (bottom), I simply cut the SPD wire, and scaled the drive voltage with a pot. It adjusts the speed to what I think is nearly 50% but there's a steep drop all of a sudden from high to low speed. Any suggestions what I might be able to do? I tried several potentiometers, all from 1K to 1M. Same.