16. A non-transitory computer readable storage medium storing one or more programs configured to be executed by a server system, the one or more programs comprising instructions for: obtaining a plurality of news stories that describe a plurality of activities performed by a plurality of other entities with whom a viewing user has established a connection in a social networking system; ranking the plurality of news stories based on a determined affinity of the viewing user for an aspect of each of the news stories; selecting a set of top news stories from the plurality of news stories based on the ranking; and determining a story layout for the selected top news stories, the story layout comprising a placement of each of the selected top news stories in one or more of a plurality of columns, the placements based at least in part on the viewing user's affinity for the top stories; providing a news feed for display to the viewing user, where the news feed comprises the selected top news stories displayed according to the determined story layout, by generating an aggregated story based on a plurality of news stories having a common topic, where the aggregated story comprises a selectable link for expanding the aggregated story for displaying the plurality of news stories having the common topic, determining the story layout for the selected top news stories and the aggregated story, the story layout comprising a placement of each of the selected top news stories and the aggregated story in the one or more of the plurality of columns, where the placement is based at least in part on the viewing user's affinity for the top stories and the common topic, and providing the aggregated story in the news feed for display to the viewing user, where the news feed comprises the selected top news stories and the aggregated story displayed according to the determined story layout.
18. The non-transitory computer readable storage medium of claim 16 , wherein obtaining the plurality of news stories comprises: retrieving a plurality of activities performed by a plurality of users connected to the viewing user on the social networking system after a last viewing session of the viewing user; determining that a first activity of the plurality of activities was performed on a previously presented news feed story comprising a second activity performed by another user connected to the viewing user that was already provided for display to the viewing user; and generating a news story comprising the first activity and the second activity.