Bukkit

Have more than one spawn point in your world!

Control biome behavior

Bukkit 1.2.5-R1.0 Version 1.0 Anti-bedrock will solve your creative pests!

Adds the players location to their tab name, so you can see where they are by pressing tab at any time!

Realistic sleeping

Spawn Eggs place Spawners. Spawners drop Spawn Eggs.

GMNP

NoFlyPvp prevents players from dealing damage to players while flying is enabled

Advanced AntiSpam

JoinMessagePlus allows you to change or turn off the join and quit messages of Minecraft.

Hardcore system designed to ban players for a duration when they die.

CR [Chat Rooms] creates an easier way to chat.

Block words, sentences, or IPs in your chat, with configurable punishments!

Plot Claim Plugin

AnvilControl

This addon simply allows you to deny any interaction (inside regions) with blocks in config

An alternate take on death in Minecraft

Make money, but if you die, you lose it all! Put your money in banks!

A plugin for Bukkit servers that adds functionality and commands to make sending whispers to players easier.

BSwear (Better Antiswear) is a very powerful antiswear plugin (with lots of words preblocked in the config)