Bukkit topic
Bukkit is a Minecraft server modification software and API, and while the original project itself is stale, forks like PaperMC and Spigot are actively maintained, and most plugins and servers use some variant of Bukkit.
Debuggery
A small plugin designed to expose API values at runtime.
intake
Easy-to-use framework for creating commands, especially in Minecraft
SportPaper
Performance-tuned Minecraft 1.8 server
commands
Java Command Dispatch Framework - (Bukkit, Spigot, Paper, Sponge, Bungee, JDA, Velocity supported, generically usable anywhere)
FastBoard
Lightweight packet-based scoreboard API for Bukkit plugins, with 1.7.10 to 1.20.6 support.
FastInv
Lightweight and easy-to-use inventory API for Bukkit plugins.
FastParticles
Lightweight particle API for Bukkit plugins, with 1.7.10 to 1.20.6 support.
ConnectorPlugin
Plugin to simplify communication between multiple Minecraft servers (and proxies) in a network. Supports plugin messages, redis and MQTT (e.g. using RabbitMQ or Google Cloud. MQTT is untested rn!). Re...
DeluxeAsyncJoinLeaveMessage
https://www.spigotmc.org/resources/deluxeasyncjoinleavemessage-fully-optimized-async-everything-open-source.88129/
NovaGuilds
Minecraft guilds plugin