Desmos Models
Tip for teachers: The key is to teach students how to build these models on their own. In doing so they learn the language of mathematics. It is less important for students to manipulate the predeveloped tools below (although in their play, they develop number and mathematical sense). Use these as models of what can be done in the classroom.
 Quadratic Function Model
 Exponential Growth and Decay
 Simple Pendulum Function
 Regular Polygon Function of Interior Angles
 Pythagorean Theorem (geometry)
 Pythagorean Theorem
 Calculating Pi with Perimeter of a Regular Polygon (lesson)
 Summation Squares

EVERYONE can learn math to the highest levelsSine, Cosine, Tangent Comparison
MISTAKES are valuable
QUESTIONS are really important
Math is about CREATIVITY and making SENSE
Math is about CONNECTIONS and COMMUNICATION
Math class is about LEARNING not performing
DEPTH is more important than speed
Jo Boaler
Mathematical Mindsets (2015)  Transforming Sinusoidal Functions
 Transforming Functions
 Vertical Motion Model
 e Function Comparisons
 Logarithm Comparisons
 Calculating the Correlation Coefficient
 Sum of a Geometric Series
 Derivatives of e
 Calculus Introduction Demo
 Riemann Sums
 Parametric Rotation of Functions
 Visualizing Function Average
Desmos Activities
Math for Pure Enjoyment
Number Talks
These Google Slides documents are not organized in any particular way. They are dynamically used with students to develop number sense. See Number Talks to learn how to implement these in the classroom.
Videos
Make oscillation patterns with salt and with math.  
Check out the interesting relationship between the period of a pendulum and its length.  
Learn how to estimate the value for pi using a circular object. 
Short Films
Use these animations to awaken a sense of curiosity toward mathematics.