Bukkit

WeatherMan

Become truly invisible in Minecraft. Zero traces. Full control.

Add magic to your server!

An mcMMO themed plugin for horse role-playing.

Stables provide steed protection, and other horse related things.

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.

An extensive questing system

Marriage Reloaded

This is a movement plugin like no other.

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

Call of Minecraft: Zombies

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

The most advanced free RPG Skills & Leveling plugin

Appear to hack to other players

FunMessages

FakePlayersOnline

aims to improve the bow vs. bow combat experience while staying true to Minecraft's vanilla mechanics as much as possible