Going beyond just polynomials, I’ve created a javascript graphing app that’s easily embeddable.
At the moment, it just does polynomials and points, but polynomials can be used to teach quadratic functions (parabolas) and straight lines to pre-algebra and algebra students. Which I’ve been doing.
Based on my students’ feedback, I’ve made it so that when you change the equation of the line the movement animates. This makes it much easier to see what happens when, for example, you change the slope of a line.
P.S. You can also turn off the interactivity if you just want to show a simple graph. y = x2-1 is shown below: