Ad-Aware 2007 released (free version)

Whats New:

• Redesigned Engine – Benefit from superior program flexibility and more accurate scanning methods with all-new program architecture.
• Improved Code Sequence Identification (CSI) Technology – Boost your privacy protection with precise detection of embedded malware, including known and emerging threats.
• Incremental Definition File Updates – Save precious time and resources with smaller update files resulting in faster download times.
• TrackSweep - Control privacy by erasing tracks left behind while surfing the Web on Internet Explorer, Firefox, and Opera, with one easy click.
• Multiple Browser Support – Choose Internet Explorer, Firefox, or Opera with expanded browser support.
• New Straightforward User Interface – Effortlessly maneuver the complexities of malware detection and removal with our new user-friendly interface.

Link:
http://www.lavasoft.com/products/ad_aware_free.php