Creatura
ElCeejo

A performant, semi-modular, Animal focused mob API

Minetest test framework
BuckarooBanzai

Provides an api to register test functions for integration-tests.

Mapblock Lib
BuckarooBanzai

mapblock serialization functions

Mana
Wuzzy

Adds a mana attribute to players, can be used as energy source for magical items, etc.

fmod
fluxionary

flux's mod boilerplate

smartshop (flux's fork)
fluxionary

a smarter and easier shop

futil
fluxionary

flux's utility mod

NodeCore Crystals
Winter94

Adds various crystal types to Nodecore

LootChests Modpack
mt-mods

Modpack adding a lot of various loot containers across the world to be found and providing an API, resources and integrations for other mods

Power Rangers Modpack
LC Creations

Adds power rangers and an API to create your own.

i3
jp

A next-generation inventory

Modding Library
LMD

Multipurpose Minetest Modding Library

AirUtils
APercy

A lib for airplanes and some useful tools

Skills
giov4

An API for creating skills.

Noriel Sylvire's Minerals Core Modpack
Noriel_Sylvire

An API for automatically registering recipes, nodes and ore generation.

Climate API
TestificateMods

A powerful engine for weather presets and visual effects. Requires a weather pack like Regional Weather.

moreblocks and stairsplus
fluxionary

adds various blocks to the game

Minetest Teams
pl608

simple multiplayer team system

hand_monoid
fluxionary

player monoid for controlling the look and abilities of the player's hand.

canonical name
fluxionary

api to get the proper capitalization of a name

node entity queue
fluxionary

a queue for spreading out the generation of node entities over multiple server steps (smartshops, signs, itemframes, etc).

craftsystem
fluxionary

API for craft registration which automatically deals w/ replacements

action queues
fluxionary

provides an API for queuing things for batch processing w/ various ways to specify the batch "size".

Cid Music Player
ekl

Plays music