This paper describes the use of the CoFIND (Collaborative Filter in N Dimensions) system to evaluate two assessment styles. CoFIND is a resource database that organizes itself around its users' needs. Learners enter resources, categorize, then rate them using "qualities," aspects of resources which learners find worthwhile, the n dimensions of CoFIND. Categories and qualities are created by CoFIND's users, so the system sculpts itself to a group's expressed needs. This paper contrasts two uses of CoFIND where students added and rated their own Web-based assignments. The first of these provided useful material to help the students with further learning goals, while the second let them use skills they had acquired in a concrete setting. The use of qualities in each instance was very different, reflecting the students' different needs in each case. Based on the results, suggestions are made for how virtual ecologies of self-organizing groups of learners might be encouraged to thrive and grow. (Contains 19 references.) (Author)