CoRank launches out of private beta this evening. It’s best described as a cross between Digg and Bluedot. It has a Digg-like user interface where users view stories, but by default you are only shown stories bookmarked by other users you’ve added as friends.

To see the whole feature list, watch the tour, here. I like keeping track of stories bookmarked by my friends (which is why I prefer Bluedot over Del.icio.us), and this may appeal to some users. For others, they’ll be just fine sticking with the services they’re already using. It’s going to be very tough for services like CoRank to get the foothold they need to grow.

Before you count CoRank out, though, it’s worth noting that the founder, Rogelio Bernal Andreo, is both a former manager/engineer at eBay and Netscape and, more importantly, is the founder of eListas and eGrupos, one of the largest social networking site for Spanish speakers. Andreo says that he plans on introducing CoRank to the eListas audience, which is 20 million strong.