Stanford History Education Group :
(includes medieval lesson plans on The Dark Ages, Expansion of the Islamic Empire, First Crusade, Ibn Battuta, Mansa Musa, Understanding the Black Death, The Black Death in Florence, Moctezuma/ Montezuma and Cortés, Martin Luther, Atahualpa and the Bible, and Galileo)
ELE Education Lesson plans, for example, Adversities in Medieval Times (ELA Grade 6)
gives Common Core standards in the Content Connections tab on the left
Magna Carta: Cornerstone of the U.S. Constitution
Edsitement National Endowment for the Humanities site, includes worksheets, assessment materials, and other lesson activities
The Crusades: Voices and Perspectives
This lesson plan from the University of Michigan comprises a 68-page pdf, giving both teacher and student resources to explore the distinct perspectives on the Crusades from Islamic, western European, Byzantine, and Jewish voices. Although aimed at 9th-12th grade, it suggests it's particularly well-suited for 9th and 10th grade instruction.
Medieval Beasts and Bestiaries
The Metropolitan Museum of Art created a lesson plan including Common Core standards and lesson activities. Although it calls upon several objects in their collection, they are linked to the lesson plan so could be explored virtually.