Bukkit

Use ezPing to see your ping or another player's ping!

InfiniteChests

NodeFly

xPermission

Better Associations is a plugin designed to associate players based on ip.

A simple plugin to display all your banned items from the config

Time-based plugin enabling and disabling and time-based command executation

This plugin adds a command which means you can heal yourself and other people!

Put warnings on players, or notes! Timestamp and formatting supported!

It allows player to report bugs or griefs to the admins on the server

My personal edit

This plugin allows you to whitelist individual worlds to control where players can go on your server...

milkAdmin - Administration/Backup/Server Data/Whitelist/Banlist

A Lightweight Memory Usage Checking Utility

Talk with other admins/operators privately!

HubTeleporter

NeosInformation

KitBlock will alert users with a customisable messages that you do not offer the usage of /kit.

A simple, fast, efficient system for automatically announcing messages or executing commands at a set interval.

With this plugin, you can make announcements on your server and also program them