Bukkit

LagMonitor

Lets you check the server lag, in ticks-per-second

A simple plugin which keeps you up to date with your current ram usage.

Detect redstone lag machines

LagLocate

LaglessWeather

Remove lag on your Bukkit server with this easy to use plugin

Remove lag and improve the performance of your server significantly with this tool!

Can Be Used To Notify A Player If They Are Lagging

Changes 'lag' to 'fun' when posted in chat.

Lag prevention made by The_Gang

LagFixer will increase your server performance! Lightweight and efficient at the same time!

LagFinder

LagEssentials is a plugin to help reduce server lag.

[] Lag Decreaser []

LagChecker For Your Server.

Check server response times!

Test whether you are in sync with the server or whether there is latency between you and the server!

Tired of players commenting on lag on your server?

Periodically remove items, mobs, and lagg on your server

Make sure the server hasn't lagged out!

All-in-one Hub Solution. Reduce player lag, save space and remove some events.

Unstick players who are glitching into the ground due to lag upon connection.

Simple, lag-free, fake op plugin that you can use to troll your players!

When a player complains about lag, and the server isn't actually lagging, will make the server seem laggy to that player.