Bukkit

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

WorldGuard

The most used authentication plugin for Spigot and CraftBukkit!

Grief Prevention

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

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

LoginSecurity

Claim land of any shape, not just within a chunk

Stops people from breaking farmland

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

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

LimitDrops

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

CoreProtect

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

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

Inexpensively protects your ores from cheaters.

bPermissions