Amazon's newest addition to the Kindle family, the Kindle Paperwhite, has a built-in light and much better resolution than its predecessors. Amazon boasts that the battery can last up to eight weeks (based on 30 minutes of reading per day with Wi-Fi turned off) and weighs less than half a pound.
If you were lucky enough to get your hands on one early, you can jailbreak it in just a few minutes. Just download the jailbreak here, upload it to your Kindle's root directory, and reboot.
Since this is a brand new jailbreak, you'll want to have a serial port on hand just in case something goes wrong and it ends up bricked. You can find more details about the jailbreak on the MobileReads Forum. Now, bring on the custom screen savers!