Online Games:
Think Fun (link to several games)
Rush Hour 
Factor Game
Product Game
Make 24

Review of Concepts:
Equations Connect Four
Jeopardy: Expressions & Equations 
NCTM Illuminations: Calculation Nation (You need to create a free account)
Algebra Nation
Quizizz
Kahoot!

Apps you may be interested in:
24 Game (how to get the app, tutorial) 

Videos/Websites:
Area of a Circle
What pi Sounds Like
Pi Day in Dominoes
PiDay.org Videos (several)
Just for Fun videos (several)
MyPiDay.com – Find your birthday (or any date) in Pi