Bukkit

Protect your horses with signed saddles.

SafeTnt is a plugin that allow you to chose what TNT can and cannot destroy

kMuteAll

Ban griefers without being online

Simple TempBan.

NoZombe disables zombe's modpack.

Disable all Invisibility Potions on your server

AutoMe! Cracked Server Protect, No Login!

iNations

AntiBypass

ServerGuard

The oldest rollback system for Bukkit

FriendlyHopper

Plugin for disabling the ability to use enderpearls.

Switch between pvp or passive mode

Hides your server essentially making you invisible for server-scanners like: ServerSeeker, Copenheimer, Shodan, etc.. simply be hiding all of your server ping data.

Use a tiered system of trust to promote players.

SlimeBall - Glues everything together

ItemDropLog

TNT Protector