FeedBurner’s FeedFlare API looks interesting. (Actually, there are a ton of Web APIs out there looking interesting, nobody could keep up.) But follow that link above and search for “Atom”; they’re abstracting the universe of feed formats using Atom 1.0 to give you something consistent and useful to write XPaths against. Microsoft’s doing the same thing in the IE7 API, but they’re abstracting to a bastardized not-quite-RSS2.0 format they made up themselves, which is kind of a confusing thing to do and will make the world learn yet another model. Atom’s popping up over in Ning-land too, they’re using the format to expose their applications and data, and are working on making it all writeable via the Atom Publishing Protocol (APP). And at ETech I heard about a couple more guerilla APP implementations, at big smart well-known outfits, not comprehensive or intended for exposure (yet) to the world, just cooked up in a hurry to get something done that needed doing. My spidey sense is tingling.