They recently took down a major botnet (Bredolab), and then notified people with infected computers. The notice included a list of recommended free web virus scanning services, which seems like a good thing to pass along:
- Panda free anti-virus online
- AVG Online Virus Scanner
- McAfee's Free Virus Protection
- Kaspersky's Free Virus Scan
Also, Microsoft's Windows Malicious Software Removal Tool