Here's an interesting thought... You're Google. You have every page on everyone's site in the world (or near as makes no odds) indexed. What more can you do with that information?

Well, how about providing a search function for that person's site? Looks like that's what the big G is thinking at the moment at any rate. Have a look at the following examples, and see what I mean.

Microsoft

House of Fraser

Marks and Spencer

Ubuntu

Red Hat 

TripAdvisor

Patterns

So far, I've only been able to generate these search boxes doing brand names searches that return sites with tens of thousands of pages, and that have sitelinks. In about ten minutes, I've been able to pull up these six, and a couple of others (New York Times and Channel 4).

Has anyone else managed to get this, and if so, what were you searching for?