The National Center was launched in 1997 to take the resources of the American Museum of Natural History directly to classrooms, informal science learning centers, and homes throughout the country. Initial efforts of this program included complete Web site experiences such as Biodiversity Counts, a nine-week middle school science curriculum. Evaluation indicated that teachers preferred to integrate select pieces of the curriculum into their existing lesson plans rather than adopt the entire curriculum. Our challenge was to keep content like Biodiversity Counts useful and available to our audience while minimizing our content development and maintenance costs. In that context, the concept for Resources for Learning emerged. Resources for Learning presents a collection of educational materials that anyone can browse or search for content to augment some learning activity. The project has established a new content-development methodology for the National Center. When a new Museum hall or exhibit opens, we produce a range of content resources and present them in a "special collection" tied to the exhibit. We can scale new content development according to available time and money, and the modular content we produce can be reused in a range of new and different contexts. Evaluation has shown that teachers find the modular content easier to appropriate and integrate into their classroom work. Future developments include a more visual display of resources to better convey the qualities of the content, and ways for visitors to collect and organize favorite resources.