What is SOPA and PIPA?
The Stop Online Piracy Act (SOPA), also known as H.R. 3261, is a bill that was introduced in the United States House of Representatives on October 26, 2011, by Representative Lamar Smith (R-TX) and a bipartisan group of 12 initial co-sponsors.

Preventing Real Online Threats to Economic Creativity and Theft of Intellectual Property Act (PROTECT IP; PIPA), also known as S.968, is a bill that was introduced in the United States Senate on May 12, 2011 by Senator Patrick Leahy (D-VT) 11 initial bipartisan co-sponsors. 

Why is this important?
These proposed bill would give the Federal government the ability to take any website offline without due process or judicial oversight under the premise of combating “online piracy.” These bills are extremely problematic and won't do much to deal with the issues they're supposed to deal with, but will have massive unintended consequences. They will lead to massive collateral damage to jobs, the economy and innovation.

Internet Blacklist Legislation
The Definitive Post On Why SOPA And Protect IP Are Bad, Bad Ideas
How SOPA would affect you: FAQ 

Who is involved?
Supporters of SOPA: RIAA, MPAA, News Corp, TimeWarner, Walmart, Nike, Tiffany, Chanel, Rolex, Sony, Juicy Couture, Ralph Lauren, VISA, Mastercard, Comcast, ABC, Dow Chemical, Monster Cable, Teamsters, Rupert Murdoch, Lamar Smith (R-TX), John Conyers (D-MI)

Opponents of SOPA: Google, Yahoo, Wikipedia, backpage, craigslist, Facebook, Twitter, LinkedIn, eBay, AOL, Mozilla, Reddit, Tumblr, Etsy, Zynga, EFF, ACLU, Human Rights Watch, Darrell Issa (R-CA), Ron Wyden (D-OR), Nancy Pelosi (D-CA), Ron Paul (R-TX)

Where Do Your Members of Congress Stand on SOPA and PIPA? 
An Open Letter From Internet Engineers to the U.S. Congress 
Obama administration joins the ranks of SOPA skeptics
Combating Online Piracy while Protecting an Open and Innovative Internet 
Under voter pressure, members of Congress backpedal (hard) on SOPA

How to be heard.
Tell Congress you OPPOSE H.R. 3261 "Stop Online Piracy Act" (SOPA) and S. 968 "Protect IP Act" (PIPA):

Contact Senate:
US Senate Site 

Contact Congress:
House of Representatives Site 
Electronic Frontier Foundation
Open Congress Emailer

If you are Outside of the United States:
AmericanCensorship.org Site