Animations Explained goes over the basics of motion, paths, etc.
Animating Custom Layer Properties has particularly clever applications of interpolation functionality: “…by overriding the -display method, we can use those properties to control anything we like, even something like sound volume….”
Custom Container View Controller Transitions goes over how to reusably package up your cool transition code.
View-Layer Synergy gets right down into the guts of how the magic actually works.
Animating Collection Views is great for sussing out how to do layout transitions.
Interactive Animations goes over how to make your animations interactive (most importantly, interruptible) via UIKit Dynamics.
While we’re on the subject of animations, you checked out Facebook’s POP framework yet? Worth a look if you haven’t. Also don’t forget that Canvas library, and the little pieces from the last little while we collected here.