- SpamBayes, a tool that filters your mail based on Bayesian classifiers. I know the technique can perform very well, but the way this system works also makes it easy to use. There's a plug-in for Outlook, but I use the POP3-filter. SpamBayes runs as a tray icon, and implements a POP3-server. My mail program (Mozilla Thunderbird) connects to SpamBayes to get email, SpamBayes connects to the real POP3-server, classifies the documents, puts the classification in the subject and/or headers, and passes it on to Thunderbird. Works with any POP3-capable mail program (that is, every mail program).
There are three possible classifications: Ham (mail you want), Spam (mail you don't want) and Unsure (somewhere in between). Via a web-interface, you can provide feedback to the classifier -- it all works pretty well!
- 12 Ghosts Popup Killer. Kills popups, 'nuff said. But it also lets you re-enable popups by pressing the CTRL-key while clicking a link or reloading a page. Also gives a short visual clue when it blocks a popup, so that you know what's going on.