Flickr announced two new features last night: clustering and interestingness. The first, clustering, is an expansion of the tags system. But now instead of just searching for photos with a tag, you can search for for photos with subsets of tags. The search algorithms look for popular combinations of tags and group them together. Going to tags/detroit/clusters/, for instance returns sub-cluters like michigan-water-river and airport-dtw-train, apparently popular groupings. The idea is that it will return groups of closely related images. Part of the fun, though, is that not everybody uses the same tag in the same way, so the clusters turn up some really interesting results. They also give you the chance to see the way other people think about grouping their subject matter.

The second new feature, interestingness, looks at the pics uploaded during a particular time perieod and returns the most "intersting" based on user responses to the pics. "User responses" hasn't been completely defined yet, but it seems to be a combination of views, tag popularity, number of comments, number of favorites, and some other metrics. You can select a month, like August, and see one photo per day. You can also click on a day in the calendar for a particular month and see the interesting pics for that day. Or, if you don't want the extra step, you can just construct the link yourself as www.flickr.com/explore/interesting/yyyy/mm/dd, and go straight to today.

Stewart says we should think of this a v0.1 release, and they'll be tweaking the features. I hope they expand interestingness in both directions: I'd like to be able to the most interesting images for a year (maybe one per month), as well as the most interesting images for a shorter period, hopefully a timestamp range with variable precision, something like 2000-12-31 23:00 EST- 2001-01-01 01:00 EST. It would also be nice to combine them, to give us the most interesting, as well as the most recent, results for any tag or cluster search. And while we're at it, why not let me see my and my friends most interesting pics, too?