Plume was recommended to me a while back by fellow TUAWer Brett Terpstra, and while it does look lovely on first site, it's one of those apps that really only shows its usefulness after a while.
Plume is a reading app (currently for iPhone only) that pulls links and content automatically from your social networking timelines, so when your friends and follows link to blog posts and other content, Plume will pull out those links and re-organize them for you in an easy-to-read form. The functionality is similar to Flipbook on the iPad, but again -- this is an iPhone app, and it rolls up this content in a way that's so unique you kind of have to get used to it at first.
Once you do figure it out, though, it's very impressive. The views are well-designed and very simple, and Plume makes it very easy to turn just a few free minutes out with your phone into a very productive catch-up session on what your friends are sharing around. I do still prefer to consume most of my content through an RSS reader on my couch with the iPad, but Plume is a great way to just pull up an app and have some popular content shown to you right away.
Plume has been updated for the iPhone 5 already, and it's available now for $2.99.