Bukkit

The first Anti-Swear plugin that uses Neural Networks.

Disguise as a mob or other player

Make your own, customized Minecraft commands

mcMMO

If you've ever used the VeinMiner mod for minecraft Forge, it has now been recreated for Bukkit, CraftBukkit, and Spigot

PrisonUtils

Change the colour of the server chat!

A Skyblock Plugin

CoreProtect

Advanced /vanish plugin which makes other players think that you're not on the server

PowerRanks

Light weight and easy to use!

a feature-rich world size limiting plugin, which can also generate or trim a world to your border

Get slimefun dusts from breaking ores!

Expand the capabilities of Skript with skRayFall

BukkitGUI - the most downloaded GUI for bukkit and any other server

A great expansion for Slimefun.

Lockette v1.4 - Simple chest and door lock, no databases!

A better way of storing items.

Schedule configurable server wide broadcasts easily