Bukkit

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

WorldGuard

The most used authentication plugin for Spigot and CraftBukkit!

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

Grief Prevention

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

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

Claim land of any shape, not just within a chunk

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

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

LimitDrops

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

CoreProtect

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

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

Provides automated plots with protection (MultiWorld support)

LoginSecurity

The banning plugin that does everything. Properly.

PlotSquared

Lightweight Protection for Chests, Furnaces, Dispensers, and more