The National Science Digital Library is a free online resource that provides high quality online educational resources for teachers and students. The NSDL has a very strong focus on the STEM disciplines (science, technology, engineering, and mathematics).
What will you find in the National Science Digital Library? Tons of high quality instructional, research, and lab materials, alongside oodles of illustrative videos. The NSDL will guide you to content benefiting educators crafting lesson plans, students struggling to gain greater understanding of a topic, or anyone with an autodidactic bent.
One thing to be aware of before you start searching the National Science Digital Library is that they include resources appropriate for a huge range of audiences, from Pre-K through Higher Education, so you’ll likely want to set the Education level before searching, as illustrated below.
Another useful feature, is that educators can click on the Standards tab to locate resources that meet Common Core and other standards.
Unlike subscription databases offered by ODIN and the ND State Library, the National Science Digital Library is not itself a content silo, but rather they are a means of discovering online educational resources from other providers. The overwhelming majority of sites linked to from the NSDL are free and open resources, though there are some that require membership or subscription (I’m yet to stumble upon any of those while using it, though).
The National Science Digital Library is funded by the National Science Foundation in partnership with the likes of the University Corporation for Atmospheric Research, Columbia University, and Cornell University.