Vocabulary.com is a site that allows you to create flashcards for any subject and you can easily assign lessons to students.
Wisconsin 9/11 Memorial & Education Center
The Wisconsin 9/11 Memorial & Education Center’s website offers free lesson plans specific to teaching students in Wisconsin about the events of September 11th, 2001. While it is specific to Wisconsin, the lesson plans can be easily adapted for any location. The site also offers field trip activities and links