Bukkit

Allow players to battle each other using custom made kits (with special abilities)

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

Private and public chat for admins

Multiple parties with GUI controls and shared inventories

BetterMOTD

Keeps track of various things such as time alive, time played, time online, and more!

Plugin for displaying command-line arguments for the server

Teleportation gates with selectable destinations

Allows filtering of commands and chats through dynamic regex usage

Notes allows appending notes onto players from staff