Fight Spam on the Internet: Includes information regarding laws, filtering, spam prevention, and responsible marketing, as well as information and advice about how to complain about spam. Laws, anti-spam information, and links to other resources

Gmail: Google-owned, web-based email service provides details of storage, options and links to related services

SpamAssassin: Open Source mail filter, written in Perl, to identify spam using a wide range of heuristic tests on mail headers and body text. Free software. Can be used as a standalone mail filter, or from procmail. Site includes download, news, FAQ, and documentation

SpamCop: Will help find the sender of a spam and an address to send a complaint to

Yahoo! Mail: Official site for the service, which features spam filters, a virus scanner, and interfaces for international users