The Morning Bell and I were attempting to conduct a PC to PC call via Yahoo! Messenger the other night, but Morning Bell doesn't have a Microphone anymore. So we devised an awesome setup that yielded great results
Since Morning Bell has no mic, I was still able to talk to him over Y! Messenger, but he could not speak back. I called him on his home phone and we both proceeded to put each other on speaker. I pointed the speaker end of my telephone to my microphone, so whatever he said on the telephone was also audiated to his computer via Y! Messenger. By putting his telephone near his computer speaker, his own voice, though delayed slightly, was conveyed in a loop, from his phone to my phone to my mic to his speakers to his phone to my phone to my mic to his speaker to his phone. Still with me?
Okay, I put my iPod Microphone (a third-party accessory I had previously purchased) under the phone so I could record the whole ordeal, and the Results can be viewed either at the top link or the bottom.
NOTE! You might want to adjust your speakers to an appropriate level, there is some pretty intense screeching.