This tutorial will show you how to build a simple player launcher to launch you about 150 blocks in the air.

You need:
16 blocks
32 redstone
A bucket of Water
Lilypad (Optional)
A button

And to load you need 15 TNT.

Watch the video (http://www.youtube.com/watch?v=HyImDmf952M) or read this:

1: Dig a 3x3 hole in the ground
2: Place water in the middle and then (if you choose to) put a lily pad on top of the source block
3: Go around the outside of the hole with redstone
4: Place any block you like (except glowstone, don't think it works with that) above the redstone
5: Place redstone on top of all of those blocks
6: Put a button down on any of the blocks and test that it works
7: Put down 8 TNT on the water blocks around the lilypad and 7 TNT on all the blocks except the one with a button on (logically)
8: Push the button, look down and destroy the lily pad and AWAY! :) You have just been launched between 140 and 170 blocks in the air!

If your player launcher doesn't look like the one in the picture above, you've done something wrong :P

The distance you travel depends on how the TNT falls down. If the written tutorial made no sense whatsoever, watch the video tutorial (http://www.youtube.com/watch?v=HyImDmf952M)

Hope this helps! :)