Apple Mac Compatible Microphones
Although many Apple computer models include a built in microphone there are good reasons for choosing external Mac compatible microphone for more versatility and higher quality audio recording options. You certainly can do a lot of basic audio with a Mac's internal microphone with reasonable quality. But for more advanced needs, an external analog mic or USB digital microphone is a better option.
For under a hundred dollars there's a wide range of studio quality USB microphones for Mac well suited to pro or amateur musicians and vocalists. These are also ideal for podcasting, or using with popular OSX music editing and mixing applications ranging from Apple's GarageBand to ProTools, Logic and other top-notch recording programs for OSX.
For models like the Mac mini or Macintosh Pro towers which lack a built in microphone, (nor an iSight web camera as well) many opt for a midrange to high-quality Mac compatible webcam that includes a mic to kill two birds with one stone as the expression goes. Logitech in particular makes some great webcams for Mac OSX Lion and Leopard that include noise canceling mono or stereo microphones as well.
For Mac Skype, other VOIP or video conferencing uses, some may opt for an analog, wireless Mac Bluetooth headset, or digital USB headset with microphone for their Macintosh voice capture needs. Just keep in mind that wired miss are often your best option - as Bluetooth range is often limited to only close distances to your Apple computer - and audio quality may suffer or cut out if you roam too far across the room.