Bukkit

This plugin is a nice tag plugin that I guess it is important in hardcore games and full pvp servers.

Share Hunger

ServerPingerAPI

BoomCraft

Sword blocking and block-hitting from 1.7

Disables the ability to drop items

MobsCanTalk is a great little fun plugin that lightings up the server with custom mob messages!

quarry

Controls world loading for Bukkit

LegendaryStaff is a plugin to show what staff you got on your server.

RoyalIRC

Mini items is a plugin, that will spawn you smaller versions of certain blocks, using certain player's heads.

Walk over blocks and let them change!

Get your position using /pos

JukeboxPlus

SectorPort

This is a API that is essential for those who would like fancy effects!

Climb Walls Like Spiders!

BattleConomy MultiWorld Economy System

Removes the potion effect upon death!