Bukkit

Vault is a Permissions & Economy API to allow plugins to more easily hook into these systems without needing to hook each individual system themselves. Vault currently supports the following: Permissions 3, PEX, GroupManager, bPerms, bPerms2, ...

The bStats Metrics class

A set of utilities for Minecraft plugins

WorldEdit Bukkit

WorldGuard Bukkit

The official self-service anti-griefing Bukkit plugin for Minecraft servers since 2011.

SilkSpawners API

Parties API

Slimefun is a Paper plugin that simulates a modpack-like atmosphere by adding over 500 new items and recipes to your Minecraft Server.

McMMO