It seems that everyone is preparing for the release of the Verizon iPhone. Those who jailbreak may know about backing up SHSH blobs, with TinyUmbrella. Basically, it's a way of ensuring that you can keep a particular version of your iOS firmware.
The latest version (4.21.07) adds support for the upcoming (though some already have it) Verizon iPhone. It's also worth noting that it works with all current iOS devices and Apple TV, and you do not have to have your device jailbroken. However, it's important to know that this is a Beta version, and we're told not to be surprised if more updates are issued.
We have a tutorial for using TinyUmbrella here.
Here are the links:
[Via The Firmware Umbrella]