Here's the story of a guy who created a DIY Skype headset with an Apple iSight camera and an old pair of Grado SR-80 headphones. It looks pretty weird though.
At first, my expectations were not high. I had the only-ever-used-as-microphones iPod headphones nearby, and I was using the laptop's built in microphone. This microphone is really close to a fan, and a particularly noisy hard drive. Not a good experience. However, I didn't have a real headset around the apartment, so I thought about how I would improvise a suitable alternative.
I needed to have the ability to get the sound into my Mac. I can't find my only microphone, and it's XLR and 1/4" anyway, so I'd have to dig out my first-rev mbox and wire that up just to get audio in. I'll put up with a little whirring and chunking (and more importantly, my colleague will put up with a little whirring and chunking) to avoid that hassle.