We've been building a hypermedia API and are likely to implement versioning leveraging content negotiation via HTTP headers. Rob Zazueta of Mashery has a great piece on this titled "The Ultimate Solution to Versioning REST APIs: Content Negotiation", mashery.com/blog/ultimate-solution-versioning-res…
Another good piece on the different ways of versioning — and how no one really has a favorite — is Troy Hunt's article "Your API versioning is wrong, which is why I decided to do it 3 different wrong ways". troyhunt.com/2014/02/your-api-versioning-is-wrong…