MacBook Air/Pro and iMacs

For an Apple Mac depending on the interface (Ethernet or Wireless) the MAC address can be found in the network preferences. For Wireless: System Preferences -> Network Preferences -> Ensure WiFi or wireless is selected on the left then select advanced -> In this page you will see a WiFi Address at the bottom of the page

For Ethernet: System Preferences -> Network Preferences -> Ensure Ethernet is selected and select advanced -> Select Hardware -> In there the MAC address is displayed