Bukkit

RandomBlockDrop is a Minecraft plugin that randomizes block drops. When a player breaks a block, it drops a random item instead of the usual one. Each block type gets assigned a random drop the first time it is broken.

AdaptiveCamo

Mendel's laws of Inheritance for sheep colors

Multiple parties with GUI controls and shared inventories

Tamed wolves but at least 10x better

BuildcraftPrivat

Logs all messages, and when Chester is mentioned, he replies with a logged message.

LightningRod adds awesome magical Rods to any bukkit server!

Call of Duty MC is a fun Call of Duty game BUT its in Minecraft :O !! Enjoy

The plugin that has all commands that can run the server!

Sajicek's TabColor and UpColor

Ultra hardcore matches with some interesting gameplay tweaks

SpoutFlight

SoundCenter adds your own music, sound effects or webradio and a simple voice chat to your Minecraft server.

Players get extra currency/items once per day!

Galaran's Heroes Skills

a simple plugin which lets you craft horse armor, saddles, nametags and now horse eggs

Angry? RageQuit Or RageQuit Others!

Bomberman for Minecraft

Complete, lightweight, easy to set up player freezing plugin.