I can't be bothered to do "proper" documentation, you can just read the source code to work things out. But I do like reference books - so here are the key functions, organised by type.
Global Objects, Lists and Functions

njin: Core Meta-OS Engine

tite: Tiny Templating

mice: Mouse, Touch and Pointer events

journey: instant navigation using pushState and hashchange

arya: Scrollable areas

blinx: Time and Dates

arty: Canvas, images, SVG

teem: Themes, backgrounds, buttons

vidchat: P2P audio/video calls

mog: Multiiplayer Online Gaming

Math: some extra methods
String: some extra methods
Array: one extra method
JSON: some extra methods