A trivial plugin that adds springs to the game.
To use a spring, stand on it, and then right click on it with an empty hand. You will launch into the air depending on the strength of the spring.
Additionally, a spring can break your fall when you land on it - again, based on how strong the spring is. If you fall further down than the spring can launch you up, it will still reduce the damage you take, but won't protect you completely.
The weak spring will launch the player up eight blocks...
The medium spring will launch the player up sixteen blocks...
And the strong spring will launch the player up thirty-two blocks.