Recommended AntiSpyware list
Lavasoft's Ad-Aware
Sunbelt Counterspy
McAfee AntiSpyware
Norton Internet Security Antispyware edition
Microsoft AntiSpyware
PC Tools Spyware Doctor
Aluria Spyware Eliminator
Computer Associates Pest Patrol*
Yahoo Toolbar with Antispy

You may notice two products recommended by other sites are not on the list. Spybot S&D and Webroot's Spy Sweeper. Both are freeware or have free versions available. Some versions available for download on the internet have been manipulated to contain spyware with the actual download, and the effectiveness of some of these products has been compermised. Both of these are good, ligitimate products that you should consider but if you do decide to download them, be sure it's from a recognized site with an established privacy policy like http://www.download.com/