I think it was Excite's search results page (defunct many years already) that had the cute feature of "search within results". I liked that feature. It seemed to me that it fit the way people think: first they look up a general term, then they start whittling it down. Having a button that allowed us to better focus in on what we wanted by adding a term (or, for that matter, subtracting one) seemed to externalize our thinking process, and I saw that as a good thing.

If anybody actually scrolls down to the bottom of a Google results page (instead of making do with the first two or three results) they'll find a link for searching within results there as well. But it seems that we're dealing with an idea whose time has come ... and gone. Google doesn't even mention that link/button on it's explanation of the search results page, and instead simply suggests refining a search through adding additional terms into the search box. Which is, of course, basically the same thing as searching within results, just a bit less stylized. But perhaps even simpler.