Google is showing an "actively discussed on Google+" link underneath some search results, which are (as you may have guessed) actively being discussed on Google+. It's unclear what the criteria are for such a result displaying this, but it is out there.
Barry Schwartz at Search Engine Roundtable blogged about the feature, after spotting some chatter about it in the WebmasterWorld forum. He shows a result for one of his own article, which shows the feature. He says it is a test, but I have been able to replicate it for that same result, so if it's only a test, I guess we're in the same test group.
If you click the "show" link, it expands to look like this:
As I said, it's unclear what the criteria are for a post to surface this feature. This particular link is from June 25, and only has one comment (also from June 25). That hardly seems "actively discussed".
Meanwhile, if you look at some of the "what's hot on Google+" content in the search results, you may be hard pressed to find one with the "actively discussed on Google+" label.
At first, I thought maybe it was only for authorship-enabled content, like Schwartz's (the reason his photo appears next to the search result), but that doesn't seem to be the case. Check out this Laughing Squid post, for example. It's currently in the "what's hot" section on Google+. It has 500 comments, including some from this morning. That, I would think, would qualify as "actively discussed on Google+". However, the result in a regular Google search provides no such feature, and it does include authorship.
Perhaps the test group lies not with a certain set of Google profiles.