Feedburner, released today the FeedFlare API. It is actually an API that allows individual develpoers to create services that "adds flare" to a feed. This extra "flare" could be either an action (like "tag this post") or additional information or metadata (like "Alexa Ranking"). They even have 101 suggestions, you could implement.
This is great news. I did not have time to look at the details, but I'm sure some really nice ideas will come out of it.
However, I still have not seen what I would like to see. Feedburner's scope is on "one feed at a time". They let you do great things, but with only one feed each time. What I would like to see is some kind of multi-feed mixing. Not there -yet?
But, I have to be fair. Feedburner is doing a great job!