A joint project between the Electronic Frontier Foundation and a bunch of American universities, this is possibly the only guide you'll ever need to the thorny problems of copyright on the web. It covers such issues as fan fiction, domain names and trademarks, defamation, parody and patents, and it's there fboth for the owners of websites to make sure they're within the law,and those who claim they're not.
It's also a repository for the notices issued by lawyers against ISPs and search engines which serve links to, or host, illegal operations that infringe US copyright laws. There's a free, searchable database which you can use to find "Cease and Desist" notices and those issued under the Digital Millennium Copyright Act naming known counterfeiting sites which use other companies' trademarks.
If you're in any way involved, as a creator or critic of material that uses known or potential copyright material, this site is a must read. And it's very cool to be able to read the actual legal notices served against companies such as Google, too.