K9 1.19

K9 is an email filtering application that works in conjunction with your regular POP3 email program and automatically classifies incoming emails as spam (junk email) or non-spam without the need for maintaining dozens of rules or constant updates to be downloaded. It uses intelligent statistical analysis that can result in extremely high accuracy over time.

http://www.keir.net/k9.html

SpamPal

SpamPal sits between your email program and your mailbox, checking your email as you retrieve it. Any email messages that SpamPal considers to be spam will be "tagged" with a special header; you simply configure your email client to filter anything with this header into a separate folder and your spam won't be mixed up with the rest of your email anymore! More than one mailbox? Don't worry, SpamPal supports multiple POP3 servers, APOP authentication, can filter IMAP4 mailboxes and can even protect an SMTP connection! Extend SpamPal with third-party Plug-ins such as Bayesian filters.
*Eugene's Pick!
N.B. this program is still in beta but is close to first release, any problems need to be reported properly so please read up on it before downloading.

http://www.spampal.org/

SPAMfighter 4.7

SPAMfighter is a free plug-in for Microsoft Outlook and Outlook Express, that automatically and efficiently blocks spam. Whenever new mail arrives, it will automatically be tested by the SPAMfighter server, and if it's spam, it will be moved to your spam folder. If you receive a spam mail that is not detected, push one button, and the spam mail is removed from the rest of the 340,000 SPAMfighters in 143 countries in seconds. SPAMfighter is available in English, Spanish, German, French, Italian, Dutch, Swedish and Danish.
N.B.this program is free for NON-commercial use & adds a tag line to your emails. The download is the FULL pro version so PLEASE READ the info at the BOTTOM of their web page before downloading the program.

http://www.spamfighter.com/Product_Info.asp

Temporary Forwarding Online

Temporary Forwarding is the alternative to Temporary Inbox. Set up a forwarding email address to use when you want to register somewhere, a website, forum or newsletter for example. all email is forwarded to your private address. As soon as you recognize you're receiving spam, you can delete the forwarding address and create a new one.

http://temporaryinbox.com/forward.php