Google Site Links are a name for additional links that sometimes show up on the SERPs under the first main result for a phrase. They are indented a bit and usually go to the site's "About" or "Contact" pages. The following article and examples seem to indicate that the domain name can play a large role in getting or keeping these sorts of results.
Google Sitelinks Increase the Value of Generic Domains, ... by a Lothttp://www.seobook.com/google-sitelinks-in...ric-domains-lotQUOTE
Google recently increased their number of sitelinks to 8 and now list them in a 2 column format. To visualize the value of this, consider that I have a decent sized monitor and only 1 listing not controlled by me appears above the fold when searching for SEO Book.