From SurfSecret Software:
SurfSecret SpamDrop is an Outlook 2000/2002/XP add-in that protects you from spam and viruses automatically. Best of all, it's free for personal use. All you need is Outlook 2000/2002/XP. (Support for other e-mail programs including Eudora and Outlook Express are on the way.) With SpamDrop, you become a member of a spam-blocking community. As you delete spam from your in-box, it gets removed from thousands of other in-boxes around the world. You receive the same benefit as a member of the community: As other members delete spam, it gets deleted from your in-box, also. Don't worry--a certain number of users have to vote for a message to become spam. This way, SpamDrop works with little or no false positives.