Essentials:
A plugin every server should have. It lets you do about 200 commands, and it's probably on of the best zombies in the world of dev bukkit.
Factions:
A plugin that lets you have base-protection. There's allies, enemies, and you can't hurt people in the same faction.
LWC:
A plugin that lets you have chest, furnace, dispenser, etc. protection. Type /lwc to see the commands.
MobBounty:
A plugin that lets you get money when you kill mobs. The money differs between mobs, so choose what mobs you want to kill!