Streamosphere tracks thousands of scientists over half a dozen social media sites and analyzes their links, likes and conversations. This page visualizes what the most popular discussions are in a particular time period.
The list view is a bit like Digg - you'll see a list of items ordered by popularity. On the left of each item is the silouhette of a person and a number. The number is the number of unique people talking about that item. You can click on the "see details" link to get a breakdown of any comments and tweets or click on the item itself to visit it.
The grid view also shows items ordered by popularity but now they're arranged horizontally by time. More recent items are further to the right than older items. Click on an item to get a breakdown of comments and tweets.
Use the see items from the past... list to change the timeframe you're looking at. You can see popular items from the past month, week, day or even the past hour.