Sometimes I try to find information about a product or an event, and I find pages that discuss about the product without providing any context: the official site, a press release, other reactions. In other occasions, I find old news: the product has morphed into something else, so my search for Writely won't produce information about the latest developments of Google Docs & Spreadsheets.
I think this is a good job for Google, that already matches ads with web pages. Google already has a product called Related Links, but you must place it on a website to see related news, videos, searches and pages. You'll also find "similar pages" for each search result, but these pages are almost the same for any page from a site and are derived from the link structure, and not from the actual content of a page.
It would be nice to have an extension or a gadget for Google Desktop that pulls all these related results on demand. There are solutions that promise to do that (pico and Y!Q come to my mind), but their performance is pretty disappointing.
Google understands the link structure of the web, so it can place a page into context, and also has the Applied Semantics technology that allows it to extract key themes of a page and discern ambiguous terms.