Lately I have been really interested in voice over IP, I think there is a lot of power in it. I was using Asterisk, but I've moved onto a much better and more powerful solution, FreeSWITCH. I was playing with it recently and decided a Caller ID spoofing interface would be fun.
When the following script is ran, it will prompt you for an access code, and if it is correct, it will let you specify a number to spoof, and a number to call. Its fun :). Also, it can send an email whenever a spoofed call is made (if you want to track your friends usage, for example).
To use the following script, put this in your dialplan: (I've put spoof.py in the fspy package.)