Thunderbird/Seamonkey addon to report spam to SpamCop, FTC, FDA, SEC, ACMA and/or Knujon.com. It also allows you to put in your own custom addresses to report spam to such as your ISP or corporate abuse address.
Good plugin for Thunderbird to report spam to multiple sources. Works well to report spam in my case to spamcop.
I like Habul, it is an easy way of sending mail marked as Junk to one of several bodies who might be able to do something about it. Spam Cop, FDA, FTC, Knujon, and evidently the Australian Government too.