Bukkit

Seeing light in your darkest hour

Allow Player's to buy land that others can't grief

Prevention of hacks and other malicious tinkering on a Minecraft server.

An extensible, player-driven, chunk protection/ownership system.

allows you to see commands being used by other users.

Allows server Owners to disable commands per-person, Per-Region, and in Groups; EVEN OPS, and Players with '*' permission!!

black-/or whitelist blocks in WorldGuard regions

All the tools you'll ever need!

Highly customizable land management for players.

A Lightweight Auth Plugin!

Protect your item frames, paintings, armor stands and leash knots! Very simple to use.

A protection system that works by surrounding an area with a material.

Saga is a combination of settlement, faction and role-playing mechanics rolled into one.

New guilds plugin! NovaGuilds!

An extremely fast and efficient logging plugin for Minecraft servers that uses its own custom database

Keep track of your users and solve communication problems

BlockLog

Simple locking solution for Chests, Furnaces, Dispensers, and Doors

Citadel is a mod that allows players to protect blocks but also allows players to break them.

LogBlock