A-Squared - Removes spyware, trojans, backdoors, worms, dialers, keyloggers and a lot of other destructive pests.  A paid version will get you real time protection and automatic updates.

AVG Anti-Virus -  No computer should be without a real time anti-malware program.  No more excuses...this one is free.

Ad-Aware - One of the first anti-spyware programs and now a full-blown anti-malware program.   The paid version will get you anti-virus and real-time protection.

Malwarebytes - Along with Superantispyware (below), this product is the best for removing the latest pests "Antivirus 2008/2009,"  "Antivirus XP" and other agressive bogus programs.  Using new detection technology, Malwarebytes is very effective and efficient at identifying and removing malware.  A paid version will get you real time protection and automatic updates.

Microsoft Security Essentials - All the basics such as automatic updating, easy scan scheduling and a simple interface are included in this free anti-malware program from Microsoft.

Norton Online Scanning Tool - This tool will allow you to scan for viruses and/or security holes on your system. (Please note that Internet Explorer is required to run this utility.)

SUPERAntiSpyware - Along with Malwarebytes (above), this product is the best for removing the latest pests "Antivirus 2008/2009,"  "Antivirus XP" and other agressive bogus programs.  A paid version will get you real time protection and automatic updates.

Spybot Search & Destroy - One of the first anti-spyware programs and now a full-blown anti-malware program.   Has some real time features but updates are done manually.

Spycatcher - Successful malware remover.  A paid version will get you real time protection and automatic updates.

Trend Micro House Call - Another online virus scanner. This one is slower but it will actually clean and delete files.