I love case studies - they're a fantastic way to learn what other people are doing and gain inspiration for your own work. I reckon you can get at least one actionable idea from any well-written case study.
But of course, they have to be good case studies. That's why I love articles like this from Econsultancy.com, 70+ Epic Social Media Case Studies, Stats, Blog Posts and More compiled by Andrew Warren-Payne.
According to Andrew, Econsultancy's senior reporter David Moth goes out of his way to dig up and analyse how big brands are using social channels". There's some great stuff in there, including: