Bukkit

MultiLink

An awesome plugin that creates a moderator support system.

SignWithLink

Highly customizable, elegant and lightweighet announcements plugin

Powerful ingame issue tracker and player ticket manager backed by SQLite or MySQL

NCPTools

Plugin that returns the block type which is in the player's target.

Simple timed announcements/news messages

StandardBooks can define written books for first join or on command

List all banned players on the server.

Rss feed reader for bukkit

A simple HTML Webserver running on the same port

MoneySQL

atsHelp

Insight

Implements a simple watchlist for Bukkit/Spigot servers

A multi-channel chat-system. Can be used as an open-source, and more light-weight alternative to plugins like Herochat.

Get all information needed from the server, players, and more, and make it all accessible in place. As well as handle players.

TwitBukkit

Need to know how to craft something? RecipeLookup is here! And it works for custom recipes too!