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.

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

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

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

Grief Prevention

Provides automated plots with protection (MultiWorld support)

The banning plugin that does everything. Properly.

LoginSecurity

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

CoreProtect

Bssentials GroupManager

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

High performance authorization plugin

Lightweight Protection for Chests, Furnaces, Dispensers, and more

CombatLog aims to punish players who log out to escape combat.

Claim land of any shape, not just within a chunk