I can't remember if it was rock or wajimba earlier today who had a mac and needed to get xfire working on it. Sadly I couldn't find the tutorial written by another sieger, but I did do some research of my own.
Mac users need to download a chat program called Adium:
http://adium.im/
The plug in for Xfire in Adium is called Xblaze.
Plug in link:
http://www.macupdate.com/info.php/id/22289
Direct link for lazy people:
http://www.macupdate.com/download.php/22289/Xblaze.zip
You should have something on your desktop now called "Xblaze.AdiumPlugin". Double click and it will install itself into Adium.
Adium may quit or lag a lot. Be patient.
When you have everything installed quit Adium and restart your computer.
Open up Adium and go to Adium > Preferences.
Make sure as well you have created an xfire account at:
http://www.xfire.com
In preferences go to "Accounts". In the bottom left corner there should be a little "+" sign. Click that. With this you are adding a new account for Adium. Scroll down and select "Xfire" and enter in your information.
I found this info from researching on google, I do not have a mac myself, someone let me know if this works for them.