The sites include the likes of the New York Times, Vimeo, CNN, and The White House. Confusingly, the Apple page does not link to the sites; it just shows a header for each. Apple has a description of how each site has implemented design changes for the iPad. Some sites like Reuters are listed as having HTML5 video for “most” content, while Virgin America is “almost entirely standards based”.
Apple also has a link at the bottom of the page asking, “Is your site taking advantage of the latest web standards?” Website admins are encouraged to submit their site for consideration as “iPad ready”. Hopefully this will be more informal than the App Store approval process.