I Skype with a standard headset/mic, the headset has two plugs (one for the speakers and one for the microphone).
huh. I have never known those to work on a mac.
Weird. Mine, a cheap headset with a microphone on a boom, works great, in both Skype and Ventrilo (a Skype-like system often used by online gamers).
I don't like using the built-in mic so much because it can sometimes pick up sound from the speakers, resulting in feedback or echo. (I Skype often with one of my sweeties who lives in Canada.)