Manually annotated data is the basis for a large number of tasks in natural language processing as either: evaluation or training data. The annotation of large amounts of data by dedicated full-time annotators can be an expensive task, which may be beyond the budgets of many research projects. An alternative is crowd-sourcing where annotations are split among many part time annotators. This paper presents a freely available open-source platform for crowd-sourcing manual annotation tasks, and describes its application to annotating causative relations.