The obvious: css-tricks.com and smashingmagazine.com
A css-tricks' curated list of animation libraries (This popped in my feed quite a while ago and I had it bookmarked)
For more curated lists: cssauthor.com (found this very recently)
AnimXYZ seems to be a great animations library if you want to get started with animations
GSAP has a bit of a learning curve, so I recommend you watch some tutorials on youtube first