Detection of elements in viewport & smooth scrolling with parallax effects.

Locomotive Scroll @ GitHub.

Ponyfill for upcoming Element.scrollIntoView() APIs like scrollMode: if-needed, behavior: smooth and block: center.
When deciding if scrolling is needed the visibility of the target element is checked. If it's less than 100% it will be scrolled.

Extremely customizable 3kb plugin for scroll based animation which animates 1000 elements without lags

lightweight jQuery plugin
for fade-as-you-scroll features

Declarative on-scroll reveal animations.

Scrollsnap allows to define 'anchor points' onto which the window snaps when you scroll through a web page or parts of it.

smart scrolling plugin.