Don’t try to market to developers. Instead, solve their problems. 

Not long ago you could count the number of 'developer marketing' programs on one hand. Now there are hundreds of programs as Web companies and enterprises open APIs. These companies know that developer adoption will make their API strategy succeed or fail. 

But Developer Marketing is an oxymoron. Developers hate marketing. 

You cannot drive adoption by 'marketing to developers.' Sure, you can send offers to your developers but your mileage may vary. 

A better formula - understand what's important to developers and give them what they need to reach these goals. Developers want to:

• build new skills that lead to the best projects and jobs. This is why new or proprietary tools and programming models are tough to get off the ground - it's a small market of new projects for the developer.
• increase their productivity. With good tools and by connecting developers with decent resources and each other for help. This is why sites like StackOverflow take off.
• be recognized for good work and see their products used. Focus on showcasing their work, not your product. It's not about you.
• get paid. Think App Store model, or affilate marketing networks.

Talk to the folks that made the big developer networks sucessful and you'll hear these points over and over. Some others:

• Developers are not buyers, but are very strong influencers. There are superstars in the developer world - make them fans and that is the best marketing you'll ever get.
• You can't 'own' or 'use' developers because they have an account on your service. Developers have lots of options and switching costs might be low from your API.
• Act on their feedback. Developers are smart and listening and acting on their complaints and ideas is critical to your credibility.
• Developer communities are fragmented. For example, there is no such thing as an "API developer', but instead there are Twitter or Facebook or Salesforce developers.

Once you have attracted a developer to use your service - they are like gold. So treat them with respect - don't try to 'use' developers or you might lose them!