Students can log in with google or clever. The can search videos and practice exercises for help with whatever topic they are working on. It will give them instant feedback on whether they are getting answers correct or not.
This is a great channel to visit to get concepts explained in an interesting way. They have a ton of videos spanning different topics, so the best way to find what you are looking for is to search in the YouTube search bar - MathAntics and the topic (ex. MathAntics equations).
There are many videos here to help students understand the topics specific to 8th grade Common Core.