From the Wikipedia article on SOPA:

Opponents of the bill include Google, Yahoo!, Facebook, Twitter, Reddit, AOL, LinkedIn, eBay, Mozilla Corporation, and Wikimedia Foundation, the Brookings Institution and human rights organizations such as Reporters Without Borders, the Electronic Frontier Foundation, the ACLU and Human Rights Watch.

The Library Copyright Alliance (including the American Library Association) objects to the broadened definition of "willful infringement" and the introduction of felony penalties for noncommercial streaming infringement, stating that these changes could encourage criminal prosecution of libraries.

On November 16, Tumblr, Mozilla, Reddit, Techdirt, and the Center for Democracy and Technology were among many other Internet companies that protested the Stop Online Piracy Act by participating in a so-called "American Censorship Day". They displayed black banners over their site logos with the words "STOP CENSORSHIP"

They had the banner up on the 16th, Mudcat has it today.