I like browsing through CodePen a lot to see what sort of things people come up with. Here's some I thought were neat. Direct link below the image. I'll make a new page when I get to 30.
Procedural Canvas Cityscape SynthWave Sun Rain P5 Dust Particles Dust Particles Augmented UI Night Drive Folder Tabs 3D Room Character Showcase Gallery Card Pagination Responsive Glitter Bank Card Pomodoro Clock Expanding Flex Cards Flexbox Card Grid Pure CSS Flip Card Water Shader 2050 World Places CSS 3D Hover Image Slider with Masking Effect Spooky To Do List Fireflies Random, Cos and Sin Dream Dangerously: Smoky Text on Hover HTML5 Fireflies Gradient Buttons with Background-Color Change CSS-only