Over the last couple of months I have begun to see a pattern, but I don't know what it's called.
The concept is that when a user scrolls to the end of the page, or a point close to the end of the main content, an animated dialog appears, usually outside the main flow in a side area. This then usually persists unless dismissed, or unless the user scrolls back up to the top.
I'm tempted to call this thing a 'just-in-time notification', because it appears just after I've finished consuming the content it relates to - but is there a better name?
You can see an implementation of this pattern here: http://mashable.com/2012/05/30/kings-social-media/
At the top of the page, there's nothing in the sidebar...
But then we scroll down, and as we reach the end of the article...
A social media / share widget pops up in the bottom right.