Ultimate Spam Blocker
This is a good spam blocker that I have found on the net. It uses a bayesian filtering algorithm to determine what is spam and what is not. During the initial few days, you have to teach the program what mails are spam mails. As the ‘learning’ progresses, soon you will find that you are receving less and less spam mails in your inbox. I have used the program for more than a month and now it filters about 99% of my spam mails. Unfortunately, right now it works only with POP3 accounts.
The program is free. If you like it, you can donate some money to the author.