Challenge students to get faster at their math facts by using Math Academy. There are different levels of difficulty so that this app is appropriate for all grade levels. Students can do time trials or build up their endurance. They earn stickers as they advance through levels.
Another math practice app, this tool gives students word problems to solve as well and they can choose from a variety of topics: numbers, addition, subtraction, sentences, money, time, etc.
Number Rack and Rekenrek
These apps are online versions of the rekenreks we have in the primary grades. However, they also allow you to cover parts of the rekenrek with shades. Students can also write on the screen. You could ask them to make number sentences, identify numbers, or find other creative uses for the write feature.
10 Frame Fill
This app is an interactive game that students can play to practice number sense. The 10 frame fills with a random number of chips and students must use counters to figure out how many more to make 10. You can change the settings to show number sentences in various orders.