I believe there used to be an official API however all the docs seems to of vanished so...
This API is used by the We Are Hunted Spotify App thus pretty stable. Reverse Engineered by @bencevans. Usage isn't to bring any harm to We Are Hunted, just for educational purposes obviously!
Base URL: http://spotifyapp.wearehunted.com/json
Base URL: http://spotifyapp.wearehunted.com/jsonp
Any request should include a callback
parameter in the querystring. e.g.
GET http://spotifyapp.wearehunted.com/jsonp/all/mainstream.json?callback=cookiemonster
GET /all/mainstream.json
GET /all/emerging.json
GET /genre/rock.json
GET /genre/alternative.json
GET /genre/pop.json
GET /genre/electronic.json
GET /genre/folk.json
GET /genre/metal.json
GET /genre/rap-hip-hop.json