Prodigy - a game based math game, students work through math problems as they move levels.
Castle Learning - select questions of various levels, for students to complete, it grades it for you, gives them hints, has banks of questions from passed regents.
Breakout EDU - use digital Breakout's to review content, create a class so you can track your students success. You can assign through Google Classroom
Quizlet - assign vocabulary content sets for students, use a variety of ways to lean the words/definitions, test on line. Can be created by teacher, use an already created one and modify it, and track your students as they work.
Freckle - a K-2 math program to work on math skills
Zearn - Hands-on math instruction. Immersive digital learning