Bukkit

A kill ranking system based on points.

LagEssentials is a plugin to help reduce server lag.

UserReputation adds a unique rep system to your server.

Prevent the wither mob boss from exploding.

Get double XP on weekends.

Control some functions creative users can and cannot do.

Get more administrative control.

PotionBoost is a plugin you can use to apply potion effects to yourself and others.