It looks like a web page, but it's a full blown web app, tied to services all over the place.
Update:the A9 diary is not a blog, it's for "[annotating] any page with notes", according to an insider.
The underlying search results are in part from Google, and in part from Amazon (the tagline at the bottom reads "Search results enhanced by Google. Results also provided by A9.com and Alexa").
The screenshot was taken with me logged in. You get access to things like a search history, showing recently visited sites, searches in the past 24 hours, and other time periods. Searches will also return results from your history, just as they will return results from any bookmarks you have.
The far right row of buttons controls what you see. Clicking the buttons displays additional columns, without any page reloading. The whole thing certainly does feel very interactive, and very slick. The application it most feels like is (perhaps not surprisingly) Google's Gmail.
The buttons control the display and search results from the following:
- Web: standard web search
- Books: uses Amazon's Search Inside the Book to return results for the terms in books
- Images: Google Image Search
- Movies: results from IMdb.com
- Reference: GuruNet results
- History: as mentioned, your own search history
- Diary: from what I can tell, this is Amazon giving you your own blog -- the URL it points to (diary.a9.com) is currently not working. You can apparently only post to it from the A9 Toolbar, which currently only works in IE.
Amazon has always been good at turning searches directly into dollars, and they've pulled together some interesting partners. I'm of course especially curious about this mysterious diary component. And the big hype word du jour -- RSS -- is nowhere to be seen.