That page on his site links to the official page, a primary source, http://judiciary.house.gov/issues/issues_RogueWebsites.html that has details on the Bill, including the actual text (PDF) http://judiciary.house.gov/hearings/pdf/112%20HR%203261.pdf
I suggest looking at this pdf, An Open Letter to Washington, http://dq99alanzv66m.cloudfront.net/sopa/img/12-14-letter.pdf & this letter https://www.eff.org/deeplinks/2011/12/internet-inventors-warn-against-sopa-and-pipa
The pdf mentions this site http://engineadvocacy.com/voice/ that makes it easy for people in USA to contact their politicians on the issue.
This link has short VOD, that covers the highlights, you may have to allow/whitelist it to show, http://www.guardian.co.uk/world/interactive/2011/dec/23/sopa-stop-online-piracy-act
I also strongly suggest reading and researching this from http://judiciary.house.gov/news/12142011%20SOPA.html:
Smith: Critics Continue to Spread Lies about SOPA
Washington, D.C. – Chairman Smith responded today to a letter that appeared in several newspapers from founders of Internet companies like Google, Twitter, and eBay regarding criticisms of the Stop Online Piracy Act. Many of the claims in the letter are erroneous and simply restate concerns that were actually addressed by the manager’s amendment released on Monday.
Chairman Smith: “It’s disappointing that some critics of the Stop Online Piracy Act do not understand what the bill actually does. The manager’s amendment introduced earlier this week narrows the scope of the bill to ensure that it only applies to foreign rogue websites. The bill defines rogue sites as foreign websites primarily dedicated to the sale and distribution of illegal or infringing material or foreign websites that market themselves as websites primarily dedicated to illegal or infringing activity. Lawful companies and websites like Google, Twitter, Yahoo and Facebook have nothing to worry about under this bill.
Please remember that while I encourage people to make their thoughts and concerns known to politicians, I believe it should be done in a Mannered, Respectful, & Polite fashion.
I have many ethical & moral reasons for that, but a pragmatic one as well, almost no one will actually listen to you, or consider your position if your Bad Mannering (BM) them!