According to the AASL (American Association of School Librarians), these are the best digital tools for teaching:
Use these tools & others in website (Best Digital Tools for Teaching & Learning) to help students with news literacy, critical thinking and other needs.
Bites is great for current events and argumentative essays.
Checkology is a digital news literacy project.
Copyright & Creativity teaches the essentials of copyright and fair use to K-12 students.
New American History is a tool for teachers and students that uses interactive maps, video, audio.
Untold collects compelling history videos and animation.
Wild Classroom encourages students to protect the environment.