Bukkit

Lucky Block Plugin

Offers full rpg system, classes, weapons, spells, mobs and quests

Build cannons out of blocks and load/aim/fire.

Craft magic potions, weed, herbs and mushrooms.

Dump all your items into one chest, and have them sorted into multiple chests, even in another room!

Optimize your server by reducing entity lag, cleaning up the world and more!

An extensive questing system

Votifier

Hide from your players! Invisibility for the distinguished gentleman.

An ore find announcer, perfect for finding cheaters.

Marriage Reloaded

A simple plugin to handle permissions, groups, prefixes and suffixes with GUI and Web Interface

This is a movement plugin like no other.

A Fully Customizable Ban Manager for your server.

Ultimate Core is all you need to setup a server and more.

Call of Minecraft: Zombies

Provides configurable options for changing damage/health for entities on your server based on Level

Manage ranked group permissions easier

Residence

Multiverse-SignPortals