Google does it automatically, using a flriay bizarre and complex algorithm to decide whether it's worth doing. They're called "Sitelinks"If you have a Google Webmaster account, it will tell you whether or not it's generated any sitelinks for your site. From that page: "Sitelinks are completely automated, and we show them only if we think they'll be useful to the user. If your site's structure doesn't allow our algorithms to find good sitelinks, or we don't think that the sitelinks are relevant to the user's query, we won't show them. However, we are always working to improve how we find and display sitelinks."