Jelly Legs is a lightweight and easy to use plugin that allows you to toggle all of your fall damage in every world.
You can also set a players permission to automatically give them no fall damage in every world
Put the JellyLegs-x.x.x.jar file in your plugins folder.
Restart the server
Open the config file found in plugins/JellyLegs
config.yml to your liking, save and exit
Check the Commands & Permissions page, to give your players access to commands/features you want them to use.
And you're done! Give me a review of the plugin here.