Math
GregTangMath - Whole Number Word Problem Generator (online or print)
Numberless Word Problems - Good for transitioning elementary students who just want to add the numbers
Computer Science
Google: Made with Code - Make a Yeti dance with block coding (great for a coding introduction)
Scratch - Program that allows for block coding practice (a step above Google: Made with Code)
Code Monkey - Learn programming in a game format (a good introduction to text-based programming with good feedback for errors)
Turtle Academy - Learn logo programming in your browser free (another good introduction to text-based programming)
Swift Playgrounds (for Apple devices only) - "A powerful open language that lets everyone build amazing apps"
Code.org - "most popular coding platform in K-12 education"