fwicki sounded good at first. Digging deeper, I'm trying to find out what the win is over tagging a group of feeds in Google Reader and having a custom feed generated from the tag. In fwicki there's a whizzy AJAX interface for grouping feeds, you have some control on the output flow of the feed "mashup", and there's a way to inject ads into/around the resulting feed. That's about it as far as I can tell.
Still waiting for a feed aggregator geared towards information foragers.