I really like the idea of River of News, dipping my toe in, and other related metaphors for consuming content on the Internet and letting it flow by.
The Drupal aggregator is sort of a river of news that Dave Winer envisions, except the aggregator isn't themable base on type of source. Feeds API is there, but I don't want items as nodes: content needs to expire and come back if it's truly important.
In my microstream I want to see:
This is probably work for Activity Stream, though it seems kind of limited in what (meta)data it pulls in.