Wikipedia
From the Telegraph:
The digital encyclopaedia will voluntarily shut down for 24 hours tomorrow (18th) in a protest against internet piracy laws in the United States.
A major target of the protest, SOPA (the Stop Online Piracy Act), has already been effectively halted by opposition from the White House, but Wales said the blackout would go ahead anyway.
Opponents of SOPA and PIPA argue they impose unfair responsibilities on websites such as Wikipedia to check that no material they host infringes copyright. Under current laws if websites remove pirated content when they are notified by the copyright holder they are not liable for damages.
The proposed laws also make it easier for American copyright holders to cut off access to foreign websites hosting unlicensed copies of films, music and television programs.
The legislation has been backed by an intensive lobbying campaign by major media owners, including Rupert Murdoch, and opposed by the giants of Silicon Valley, including Google and Facebook.