Bukkit

WorldEdit is an in-game map editor for both creative and survival

WorldGuard

The most used authentication plugin for Spigot and CraftBukkit!

Open anyone's inventory as a chest in real time!

Grief Prevention

The premier long-range map editing tool for Minecraft SMP.

Claim land of any shape, not just within a chunk

Backup and restore your server with ease. [aupports FTP]

Guilds, war, land claiming, and user-controlled antigrief

LimitDrops

Stops people from breaking farmland

CoreProtect

LoginSecurity

Detect and fight the exploitation of various flaws/bugs in Minecraft!

Advanced /vanish plugin which makes other players think that you're not on the server

a feature-rich world size limiting plugin, which can also generate or trim a world to your border

Lockette v1.4 - Simple chest and door lock, no databases!

PlotSquared

The banning plugin that does everything. Properly.

Provides automated plots with protection (MultiWorld support)