This post will record my experience completing the Getting Started Instructions for the Xilinx Zedboard using a MacBook Pro.
Follow the instructions as listed from Xilinx (plug it in, USB cable to UART port, insert card, power-on) to step 7.
The only tricky bit was creating a Virtual Terminal on the Mac. The Cypress UART driver is already installed on most modern macs. Open a terminal window, identify the UART device, and connect to it with screen as follows:
ls /dev/cu.usbmodem* screen /dev/cu.usbmodem1141 115200 -L
Now continue with step 8. reset power to the board on the board and you can watch it boot!