MacScan an anti-spyware program for OS X is free today.
All you have to do is download and run the 5.1MB installer. When prompted, click ‘purchase macscan’ and enter the coupon code ‘PIRATE’ during checkout.
The download, install, purchase and registration must all be completed by Monday, September 20th 2010 by midnight PST.
Download at: http://macscan.securemac.com/download/