If you want to feel like you're jumping on a trampoline, you might want to use a Slime Block to cushion your fall. Simply collect nine Slimeballs to make one Slime Block. You can now place a Slime Block, then jump on top of it from a great height. Assuming you hit the centre, you'll bounce on it without taking any fall damage.

Initially, the bounce will be 60 percent of the height fallen but this reduces down to about 20 percent as the height fallen increases. If you jump as you land your fall damage will be entirely negated but the blocks bounce effect will also be ignored. Jump make sure you don't hurt yourself when you bounce off.