Crowdsourcing is an umbrella term for a variety of approaches that tap into the potential of a large and open crowd of people. So far, there is no systematic understanding of the processes used to source and aggregate contributions from the crowd. In particular, crowdsourcing organizations striving to achieve a specific goal should be able to evaluate the mechanisms that impact these processes. Following a method of IS taxonomy development we propose a new taxonomic framework for crowdsourcing processes. In contrast to previous work, this classification scheme focuses exclusively on an organizational perspective and on the mechanisms available to these organizations. The resulting dimensions are preselection of contributors, accessibility of peer contributions, aggregation of contributions, and remuneration for contributions. By classifying the processes of 46 crowdsourcing examples, we identify 19 distinct process types. A subsequent cluster analysis shows general patterns among these types and indicates a link to certain applications of crowdsourcing.