Micro-task markets such as Amazon's Mechanical Turk represent a new paradigm for accomplishing work, in which employers can tap into a large population of workers around the globe to accomplish tasks in a fraction of the time and money of more traditional methods. However, such markets have been primarily used for simple, independent tasks, such as labeling an image or judging the relevance of a search result. Here we present a general purpose framework for accomplishing complex and interdependent tasks using micro-task markets. We describe our framework, a web-based prototype, and case studies on article writing, decision making, and science journalism that demonstrate the benefits and limitations of the approach.