MAC Spoof on OSX

macspoof.sh

# Do these once
ifconfig en1 | grep ether > .macaddress      #Save your real mac address somewhere

# Alias the airport adapter
sudo ln -s /System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport /usr/sbin/airport

# Then each time you want to change MAC address:
airport -z                                   #disconnect but don't turn off the airport
sudo ifconfig en1 ether 00:00:00:00:00:00    #set new mac address (perhaps just increment your old one)
ifconfig en1 | grep ether                    #check it's actually changed

# And you're done