From SmashWiki, the Super Smash Bros. wiki
The spring is an item in Super Smash Bros. Brawl. It was confirmed at E for All. Originating from Donkey Kong Jr. and Super Mario Bros., it propels a character skyward when jumped on. It can also land sideways, which causes anyone to bounce to the opposite side of the board. The springboard can be picked up and thrown. It can also be useful for launching other characters off the screen.
If a character is close enough to the upper boundary of the screen, and another player throws the spring straight up, it can act
as additional launch; if the victim hits the actual spring and is launched upward, of course.
When thrown straight down, it causes the character who threw it to bounce off of it, restoring all of their jumps midair, as seen in this video:
http://www.youtube.com/watch?v=GesiZLX-45o
[edit] Trophy
An item used to assist jumping. Jump on it, and it will send you bounding sky-high. You can also toss enemies onto it. It originally appeared in the second stage of Donkey Kong Jr., where it was used as a shortcut to leap to a distant platform. It resembles the bouncing projectiles that appeared in Donkey Kong, but those are said to be actually jacks, not springs.
