Kevin kelly has come up with a name for all of these collaborative bookmarking/link submitting/link rating/link commenting sites. Kevin writes about how social networks and algorithms are being used to filter, rank and rate content:
These new uncategorized sites, which have emerged this year (and reviewed below), fall in between the positions above. They take the smart mob approach of MetaFilter and add the algorithms of search engines. So, readers themselves vote on the importance of linked items suggested by other readers; these votes are then subjected to a complex formula to produce rankings. The sites use various flavors of algorithms to balance and refine the votes and selection of smart mobs. Or they use the action of tagging or bookmarking a site as a type of vote. Each site uses a different algorithm, yielding slightly different mixes of links, and a different personality. The best sites maintain a balance between providing a sense of what everyone is reading (consensus popularity) and some novel items that not everyone is reading (yet). In the reviews below I try to capture some sense of distinctive style for each site.
Kevin has a great list of sites that do this and explanations of how each work.
Link via the illustrious search genius, John Battelle.