This is outdated, I'll be deleting the "simple screensaver hack" soon. I made it as a proof of concept since many people are asking "where's the touch hacks" after the jailbreak came out.
Check this out:
http://yifan.lu/p/custom-screensaver/
Also, 5.0.3/4.0.1 jailbreak:
http://yifan.lu/p/kindle-touch-jailbreak/