The latest to try is Hawthorne Labs, a nest of former Google and Bing engineers who have produced Apollo, a publication that draws upon user patterns to choose what might be preferred from various categories. Apollo helps the user discover content.
It uses an algorithm to hunt blogs, social media and traditional sources to cluster content of interest to someone on the basis of her online roaming. It's an interesting project worth noting. An iPad application is out and an iPhone app is coming.