Bukkit

Allows you to recolor glass and hardened clay in the world as well as scrape off the dye.

SoundBoard adds the ability to play sounds to other players

TexturedSpout

A welcoming message to the server with a reward for joining the server.

Better Death

AntiMobSteals is a plugin that aims to protect player's mob kills from being stolen.

GameModeAX

A plugin that allows you to quickily make an ingame voting screen for whatever you need

A plugin which adds some mechanics which make game harder

This plugin will execute a command from console specified on a sign

Any flammable block that catches on fire burns until it is destroyed.

An advanced whitelist tool.

Fully customize weapons, armor and tools with custom RPG stats with custom damage types, custom defense types, 25 item stats, and tons more options.

Display your death coordinates in the chat.

TownPortal

Create your own classes and request work from students in return for reward based on grade

Notifier plugin for Towny, warning users about building in plots they don't own

Teleport easily to another player!

A plugin that lets players consult a log of their protected chests, along with the info of the player who destroyed them!

A plugin with stuff (commands) that might be useful I think