As per usual, Apple makes it just slightly harder to accomplish things that windows and linux do with flying colours.
This video shows you how to create a micro-instance of Amazon on your Mac:
Another great option for those of you who are using Macs, is to look for other programs which can accomplish similar tasks to NodeXL.
One great example is Gephi, an opensource software designed to generate and export lovely looking graphs.
On this page, you can find both the download links and information for installing on Windows, Mac or linux.
This page offers some great intro tutorials for working with Gephi.
I hope you all enjoy!