It is really hard to find people who are using this in interesting ways beyond mere RSS aggregation, so I was wondering if anyone had some good broadcasts to recommend.

So far, I am only subscribed to Pro Publica: https://app.net/c/2wtz.

YC also have a bunch of them: http://blog.ycombinator.com/subscribe-to-y-combinators-broadcasts-via-app-dot-net.