Last year, people started to notice that Google began showing "subtopic" or "subcategory" links below their listing, if they were the first in a Google search. Now, Google's finally confirmed the change as a permanent feature and given it a name: sitelinks.
Here's an example of sitelinks in action, which I tapped into doing a search for HP:
Notice how under the first result, there are a number of sub-listings, such as:
Software & Driver Downloads - http://welcome.hp.com/.../us/en/support.html
Contact HP - http://welcome.hp.com/country/us/en/contact_us.html
Jobs - http://www.jobs.hp.com/
Small & Medium Business - http://www.hp.com/sbso/
Those are sitelinks, and now named via the Information about Sitelinks post at the Official Google Webmaster Central Blog. Do the search, and you'll see only the first result gets them (you'll also notice that Google is failing to remove the second www.hp.com listing as it should -- only one major listing per web site per results page should be showing. I think there's a bug, at the moment).
How do you get sitelinks? You have to be in the first position for a search. Aside from that, whether they'll still then show up and exactly which ones show, if so, aren't explained. Here's the new help page on that.
Want some clues? Try looking at our Google Web Site Categories Explored post from earlier this year.
Want to comment or discuss? Visit our Getting New Sitelinks Under Your Top Listing At Google thread at the Search Engine Watch Forums.