I was all excited to try out Yahoo Pipes, which Tim O’Reilly calls “a milestone in the history of the internet” (not bad for zero day software), but of course it was down.
Judging from the screenshots I’ve seen, the concept is similar to smart playlists for iTunes. It allows you to filter the content from individual feeds based on a set of feed properties, and then combine those feeds in interesting ways. For example, now you can screen out posts from all of the authors you dislike on group blogs.
One interesting aspect of Pipes for site creators is that if it takes off, they can look at how users are taking advantage of their feeds, and then apply that knowledge to making their sites better for everyone.
Read Jeremy Zawodny for an overview and a bunch of outbound links to other comments about Pipes.