SpamAssassin is an excellent free utility for detecting spam in your e-mail. You can now use bayesian filters to seperate "the ham from the spam" based on statistical models based on your own mail.
The MAPS Realtime Blackhole List was one of the first blackhole lists for rejecting mail from rogue SMTP relays.
spam.abuse.net provides a good listing of tools to block spam, legal information, and more.
Habeas sender warranted email adds a copyrighted phrased in the headers of messages to guarantee that they are spam. Spammers who use this message can then be sued for copyright infringement. One hopes they do, since a number of spammers have started to use the headers...
Spam Laws provides a comprehensive but easy to browse list of spam laws world wide
We must be careful not to forget the wonderful lunch meat for which bulk email was named.
Telemarketers
The National Do Not Call Registry actually appears to work in stopping telemarketers. Unfortunately, political organizations and companies that you have previously done business with are exempt.
Bulk Snail Mail
The Mail Preference Service is a list run by the DMA to have your name removed from customer mailing lists.
Miscellanea
Search Google News for articles relating to spam in the press. Hardly a minute goes by...