Bukkit

Chest lock

Simple whitelist enabling Bukkit

A friendlier alternative to kick

A plugin that banns Mc-Leaks accounts on join.

Emergency

A free anti swear plugin for a swear-free server!

Remove all minecarts with one command!

bReport

Simple plugin that restricts the use of TNT

WorldGuard TreeFarm Flag

Stop Bots and Spammers from joining and spamming IP's.

BanRecipe

Freeze bad players and stop griefers!

Stop breaking and placing of blocks if a player doesn't have a permission

Disable and track TNT/Lava griefers!

RudelTools

Juke Alert is an add on to Citadel that lets you create snitches.

GriefPrevention-Anti-Worldedit

This very simple plugin prevents players from pvp logging. Players can't use commands while tagged and die if they log!

Stopping those hacks on your Bukkit server.