Where is the web animation community on the Internet?

If you mean javascript/css animation effects then there are a lot of cool demos at:

https://codepen.io/search/pens?q=animation

https://dribbble.com/shots/popular/animation

For webgl there's:

https://www.shadertoy.com/results?query=&sort=popular&filter...

https://experiments.withgoogle.com/search?q=WebGL

And for codegolfing, there's https://www.dwitter.net/top/all which restricts you to 140 characters or less.

If you mean the flash-animation community, I also wonder where they disappeared off to. I felt like they peaked in the mid 2000s. Now you just made me remember some newgrounds movies that I am going binge watch for nostalgia now: "There she is!!"(2003) https://www.youtube.com/watch?v=WsWgrf3XLKQ