This paper reviews a wide range of scholarly and popular literature to provide an overview of the current state of online user–generated content (UGC). We describe the UGC value chain, introduce three varieties of content (creative content, small–scale tools, and collaboratively–created content), and describe the factors unique to each variety. We then identify the common elements across varieties: motivations for content creation, mechanisms to support content creation and control content quality, and value creation. Throughout the article we identify the interrelationships between social and commercial forces on UGC creation and distribution.