AideRSS is an intelligent assistant, which continuously monitors RSS feeds, finds the good stuff, creates a PostRank, and delivers it to you. The philosophy behind our API is to provide full functional parity of what users see within MyFeeds and our widgets. Currently you can retrieve the Top Posts, Feed Stats and Entry Stats for a given Feed ID. In addition you can retrieve the actual RSS Feed with the PostRank RSS Extension for a given feed.
AideRSS, an RSS feed filtering service, has recently made available a public API. The AideRSS tagline is 'Read what matters' and their mission is to "research every story and filter out the noise, allowing you to focus on what matters most."