Web curation involves choosing, organizing, and commenting on content. Popular web curation apps-e.g., Facebook, Twitter, and Pinterest-provide linear feeds that show people the latest content, but provide little support for articulating relationships among content elements. The new medium of free-form web curation enables multimedia elements to be spontaneously gathered from the web, written about, sketched amidst, manipulated, and visually assembled in a continuous space. Through free-form web curation, content is collected, interpreted, and arranged, creating context. We conducted a field study of 1581 students in 6 courses, spanning diverse fields. We derive patterns of free-form curation through a visual grounded theory analysis of the resulting dataset of 4426 curations. From the observed range of invocations of the patterns in the performance of ideation tasks, we conclude that free-form is valuable as a new medium of web curation in how it supports creative visual thinking.