Google "Sitelinks" are those which can be most often found just under the first result for a branded search term. See below for the SER listing which includes Sitelinks:
A recent post at Sphinn by Laura Callow links to an excellent overview of how Google Sitelinks are handled, and the article can be found at SEM Insights: How to Get & Influence Google Sitelinks (Organic). Sitelinks have been discussed here and within other forums and blogs for some time, but continue to confuse people. The bottom line is that you can try to influence your Sitelinks, but you cannot directly choose the ones that will be granted to your brand listings.
As Laura mentions in her article, you cannot request specific Sitelinks, but you can block the ones you don't want in Webmaster Tools. We continue to ask for them to replace the link with a specific recommendation, every time we block one and Google asks why, but we cannot confidently say that those suggestions are given credit or consideration.
I would also add that there does tend to be a lag between the Sitelinks reported in WMT and the ones that are actually live. Usually, the changes are made live in the search results prior to them being updated in the Webmaster Tools report, although I have seen a couple times this year it happening the other way around.
Please share your thoughts and experiences at Sphinn or SEM Insights.