Brainpop.com – With a subscription, I am able to show various animated math videos as a good introduction to topics. There are also simple quizzes to go with each topic.
ixl.com – This website has great drill/skill practice for any math topic from PreK – PreCalculus as well as some Language Arts, Social Studies and Science. The questions will progress in difficulty as the students correctly answer them. When questions are answered incorrectly, an explanation is provided on how to do the problem. My district has a subscription for this site so I am able to track my students progress and assign topics throughout the year. There is a free trial time.
Nearpod – Interactive lessons can be created where the students can work on the material using their individual devices. Many types of activities can be created to keep students engaged.
Plickers – This free website allows the instructor to create multiple choice/true false questions to be presented to the class. Then through the use of a smart phone, students answers are scanned and recorded. It is a great tool to get instant feedback on student understanding and keeps all students involved in the lesson.
Socrative.com – Various types of quizzes or games can be created for any topic using several question types (multiple choice, matching, drag and drop, true/false).