Here are some useful links to utilities that can help you in the fight against unsolicited (spam) email.
Advanced Email Protector
Add a new weapon to your e-mail arsenal with Advanced Email Protector, which runs your messages through a multistage filtering gauntlet before they finally reach your mailbox.
Bounce Spam Mail
Fool those spam mailers with this program. Send a fake bounce message back to them, making their targeted mailing list manager think your address is invalid. Works in many cases where you can't get to the real sender of the message.
This is a multitalented network query tool with extra utilities built in to handle spam mail. It includes typical utilities such as ping, traceroute, whois, and finger.
This is a great tool for UNIX and Linux users. It is a mail filter which attempts to identify spam using text analysis and several internet-based realtime blacklists.
This junk e-mail killer runs from the system tray and deletes spam before it ever gets to your mailbox. Filters for more than 15,000 spammers are included. You can easily configureSpamBuster to filter up to 12 mailboxes.
This site is a mixture of filtering tools and guides to reporting spam that acts as an electronic doorman as well, letting you know when an unknown guest is e-mailing you.
This tool lets you add your own addresses to your blacklist, or use the included blacklist of known spammers to prevent spam from ever arriving in your inbox. SpamKiller features automatic updates of the included blacklist and the ability to send an automatic message to the spammer to request your removal from the list.
This anti-spam product comes with predefined keyword lists and domain lists, which you can modify to add your own. You can set filters to specify when to reject or keep a message.
Use Spammer Slammer with Eudora or Netscape Mail to filter out spam quickly and easily. It automatically configures itself, and even works with multiple e-mail accounts on the same computer.