David E. at our forums spotted Google using a "note this" feature next to the cache link in the Google.com search results.
I spotted a screen shot of this over here, so I cropped it out to show you here.
I do not remember ever seeing this feature.
From the thread, I learned you have to be logged in to see this new feature. I currently do not see it, even when I am logged in. So I suspect this is some sort of feature Google is testing.
When you click the "note this" link, I am told it then shows that search result as being "duely noted."
Probably a way to "star" things or save search results for later. But I am not sure as of yet.
Forum discussion at Search Engine Roundtable Forums.
Update: As the comment says below, it may be related to Google Notebook. Maybe I do not see it, because I don't use Google Notebook. But there is a Google Blog entry named note this.
