Mac AntiVirus: ClamXav.com
ClamXav is a free anti-virus package for Mac OS X which, as of today, supports Jaguar (10.2) through Leopard (10.5). VU versions for Jaguar and Panther (10.2 and 10.3) are unsupported, but Tiger and Leopard are actively maintained, Universal Mac applications. Go to the ClamXav Download Page to get your version. I liked this flavor of antivirus for the Mac because it is based on the ClamAV open source antivirus toolkit for UNIX. You can learn more about the Clam AntiVirus toolkit from their website, and this is a standard option in most Linux distributions. After you download the disk image file, simply drag the ClamXav application to your applications folder and run it from your hard disk. The first time you run the program, it will ask to install the ClamAV Antivirus engine. After you run the separate installer, you’ll need to start the program again. Take a moment to update the virus definitions, and then run a scan on any folder or volume on your Mac.