It seems like Google is now rolling out the carousel based sitelinks they have been testing for over a year now. Instead of showing basic text based links under the search results snippet, Google is now showing boxed-in sitelinks that you can scroll left to right through in a carousel-like interface.
Here is a screen shot I was able to generate myself:
Sergey Alakov tracks this stuff pretty closely and he said it is rolling out and posted so also on Twitter. Also based on all the people emailing me about this new feature being tested, I believe it is no longer a test but indeed rolling out.
I emailed Google for an official comment and hope to hear back soon.
Forum discussion at Twitter.