COMODO is a leader in internet protection. They cover the range from home users to large enterprise setups, to issuing security certificates to web domains. They have a range or free products for Windows, and some for Mac, and here is a short list/description and link to their products:

http://www.comodo.com/home/free/free-protection.php?track=2767

Internet Security – includes antivirus, firewall, malware protection, and other features

Anti Malware – Detects and removes various malware

Antivirus – detects and removes various viruses, worms, Trojans…

Firewall – protects against online attacks against your system

Secure Messaging – protection for instant messaging

BackUp – make a backup of your system. Includes limited online backup storage (additional storage available for a fee, or with paid version)

Dragon – a Chromium based browser with additional security features

Programs Manager – watches the system as programs are installed, so that they can be completely removed later

System Utilities – items such as disk optimization, registry cleaner, and more

Cleaning Essentials – locates un-trusted processes and lets you stop them

NOTE: Some, but not all of the above items have a paid, commercial version with additional features that you may or may not find useful. Make sure that you download/install the version that fits your needs.

http://www.comodo.com/