Here is what I have found this late evening. The Developer Evangelist Handbook is something which is a good read from one side and serious role at every IT company.
This handbook will get you on the way to be a great developer evangelist for any product or company. Of course your approach needs tweaking for different markets and audiences – and in accordance with your own personality – but the main principles are the same for everybody and anywhere in the world.
Developer evangelism is a totally new field of work and the first hurdle you will encounter is people asking what a developer evangelist is and why any company would need a role like that.