Since then I have had a few comments from readers asking about how to create your own cable for PF motors to control it from a NXT. So here is instructions on how to create your own cable in 2 minutes.
Please note that this method of driving the motor from NXT is not endorsed by LEGO and also exercise caution when working with knives and cutters.
Step 1: Start with a NXT cable and a PF motor.
Step 2: Cut the end off the PF motor and also one end of a NXT cable.
Step 3: Use a sharp knife to extract the two central strands in the PF cable and the black and white strands in the NXT cable. You can cut off the remaining strands and discard as shown below.
Step 4: Remove the insulation from the strands as shown below. This is best done using a wire stripper. Don't be tempted to use your teeth - as you will get used to using your teeth and it is a hard habit to kick.
Step 5: Twist the wires together as shown. It does not matter which way (as you can control the polarity (direction) from the NXT - but if you are doing multiple wires, be consistent so you can use the cables interchangeably.
Step 6: Use an insulating tape to ensure the two exposed strands are not touching each other. Wrap it up to make it look neat. You need to tape it around about 4- 5 times so the wires dont come apart during normal use.
Step 7: Incorporate the PF motor in your NXT creations and start enjoying it!
Other Tips: If you have a soldering iron, you can use it to make the connection better and stronger by soldering the strands together. Also if you got a heat shrink, use it to give the cable a professional looking finish. And lastly, you can use the PF motor and the other end of the NXT cable to create a PF motor with NXT end in addition to a PF adopter - so you have no wastage.
If you are really experienced in making cables and got some suggestions, feel free to add your comments and tips below.
Edit: The other option (if you dont want to butcher a PF motor) is to use the PF extension instead of a motor for PF connector source: Then you could build 2 NXT compatibility cables, one of them beeing dual duty (PF and 9V). Thank you Philo for the suggestion. Also you can read about Philo's excellent guides on creating various custom cables in his web site.