Arena_lib
Zughy

Library working as a core for any mini-game you have in mind

futil
fluxionary

flux's utility mod

Minetest Teams
pl608

simple multiplayer team system

Mapsync
BuckarooBanzai

Synchronize the ingame map with a lua-backend

Flow
luk3yx

A formspec library that automatically positions and sizes elements

mtzip
BuckarooBanzai

zip-library

Mapblock Lib
BuckarooBanzai

mapblock serialization functions

Giad
ekl

WIP Library for creating walking vehicles

craftsystem
fluxionary

API for craft registration which automatically deals w/ replacements

Power Rangers Modpack
LC Creations

Adds power rangers and an API to create your own.

fmod
fluxionary

flux's mod boilerplate

moreblocks and stairsplus
fluxionary

adds various blocks to the game

AdvTrains Livery Tools
Marnack

Livery tools for Advanced Trains mods.

Mob Core
ElCeejo

A Mob API meant to expand upon mobkit and bring easy to use features for creating new Mobs.

smartshop (flux's fork)
fluxionary

a smarter and easier shop

Comboblock
sirrobzeroone

Allows the stacking of slabs vertically and horizontally

Advanced Biome Decoration API
EmptyStar

An API for creating advanced, complex biome decorations

Luamap
MisterE

An easy-to-use api for lua mapgens that takes the pain out of mapgen coding. Focus on mapgen logic, not on voxelmanipulation.

AirUtils
APercy

A lib for airplanes and some useful tools

Library Mount
Panquesito7

API Framework for mounting objects.