Bukkit

A simple plugin that allows you to have per world motds.

EpicAutoMessenger

Ranger - remember, forget, and find locations

A simple HTML Webserver running on the same port

MineStats | Minecraft Statistics plugin with Web Stats.

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

MobHealthDisplay

MessageJoin

UUID allows staff members to check a player's UUID.

A guide to resale values of blocks or crafted items

Customized Repeating Messages Made Easy

Captain'sLog

Easy Prefix is a possibility to use prefixes without permissions.

Gives Ram usage, temp, etc. Alerts you if ram usage is too high

Chunk Viewer

Web interface for CoreProtect

Reddit

MOTD plugin

Adds the extras which most plugins don't have to your server

Teleports players to spawn when joining, and sets their selected slot.