Narendra Rocherolle and Nick Wilder, a couple of the hackers behind the long in the tooth Webshots, cooked up Shoebox, a "vertical" social bookmarking and aggregation application. Shoebox is for bookmarking images on the Web, and watching webfeed streams of photos. Pursuant to its focus on images, Shoebox has a decidedly different presentation style. I think there are any number of applications like Shoebox, which ride on top of the webfeed ecology, but to the average user, don't look anything like an aggregator.
Shoebox development has a blog and Rocherolle's contains a lot of insight into Webshots, which is way older and way bigger than Flickr.
Memo to Webshots. Flash popunders are exceedingly painful. Please make it stop!!