Essentials by Antonio Noack
You may know Essentials as Minecraft plugin but what is important here is its name: is includes all the commands that make your life easier.
DevKit by Antonio Noack
The DevKit, developers kit, allows plugin and mod creators to build their creations near the game itself without need to upload the files every time. It works since the files are loaded from the game itself. There is an editor in a second tab when you use the command /openeditor or /oe.
WorldEdit by Antonio Noack
Yeah right, just like the bukkit/spigot plugin, there is a WorldEdit plugin for your server on play.phychi.com now :)