The National Library of Virtual Manipulatives is a library of free K-12 resources for math teachers. It’s worth checking out if you have an interest in instructional design regardless of the particular subject or level that you teach. There are some very clever ideas for learning objects here. Plus, you gotta give them credit for the name. “Virtual manipulatives”…I love it!
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The views expressed here are solely my own and do not necessarily reflect those of my employer.