CNET has a FAQ on "How SOPA would affect you."
Kos has more information about the bills and their sponsors, a graphic of what could happen, and links the New York Times and Los Angeles Times editorial.
Balloon Juice has further discussion.
The ACLU has posted "Good Idea, Poor Follow-Through: Congress' Mistakes with SOPA," a post on the Congressional hearings on the bill,
"Free Speech Takes a Beating," and their statement for the record at the House hearings. From the first link:
The Stop Online Piracy Act (SOPA), introduced by House Judiciary Committee Chairman Lamar Smith (R-Texas), while a well-intentioned effort to reduce online copyright infringement, is severely flawed and has much broader implications than its Senate predecessor, PROTECT IP. Copyright protection is absolutely vital to free speech in that it encourages innovations and assures creators that their work will be protected; however, it is extremely important that such protection remains consistent with constitutional principles and only impacts those who illegally use protected content. SOPA’s vague definitions could lead to the restriction of completely lawful non-infringing content...
Under SOPA, the attorney general would be able to identify an Internet site that is ‘committing or facilitating the commission’ of online copyright infringement and then serve a court order which would force Internet service providers (ISPs)to block access to the accused site. The court order would also compel payment network providers, Internet advertising services and search engines to sever ties with the website. SOPA also allows victims of copyright infringement to take action independent of the courts by directly sending notices of infringing content to Internet advertisers and payment processors. The advertisers and payment processors must then follow the same steps to sever their connections with the infringer as they would if the notice came from the attorney general.
While this all sounds productive and effective in theory, the lack of narrowly tailored language could essentially lead to the shutdown of sites that contain very little infringing material. SOPA also fails to assure that those whose material will be blocked, whether infringing or non-infringing material, receive adequate notice before the content is blocked. We agree that online infringement is a continuing problem, but we do not believe that it is acceptable to sidestep procedural protections, especially in cases that may involve non-infringing First Amendment protected material.
So what does all this mean to the average Internet user? Many opponents fear that the sites that would suffer most under SOPA are those with primarily user-generated content, such as Facebook, Twitter, and YouTube. For example, Katy Perry could decide that the awesome video you just posted on YouTube rocking out and lip-synching to her latest hit was, in fact, copyright infringement. All Ms. Perry would have to do is notify YouTube’s ISP of the supposed copyright infringement, and YouTube’s entire site could effectively disappear from the Web, perhaps even before YouTube was notified and despite the fact all other content on the site was non-infringing. Fear of an entire website being taken down for such a small piece of content could lead such user-generated websites to police their users’ content, thus impeding free speech.
For what it's worth, SOPA seems to be a worse bill than PIPA, but elements of PIPA still raise serious concerns.
Senator Ron Wyden (D-OR) is asking for names to petition Congress and to read during a potential filibuster of PIPA. The ACLU (for SOPA), Electronic Frontier Foundation and several other sites have petitions as well.