Funded by the National Science Foundation, the National Science Digital Library is a collection of resources for education and research in the areas of science, technology, engineering, and mathematics. The resources are organized in multiple ways, so you can find resources by topic or by target audience.
The content isn’t developed or maintained by the NSDL. It’s just an index of resources hosted elsewhere on the Internet. Because the resources are specifically chosen for inclusion in the collection, and are well indexed, it does make it easier to find accurate, appropriate, and relavant information for teachers and students at all levels.