Just a few days after the release of the untethered 4.3.1 jailbreak, the iPhone dev-team has released a new version of Redsn0w (Redsn0w 0.9.6rc11). This release will bring things such as boot animations, less unnecessary options (such as the removal of options related to the side switch on the iPad which has no side switch), and a cleaned up GUI. It will still include no support for the iPad 2.
Redsn0w 0.9.6rc11 will also allow for you to jailbreak your iPhone over an existing jailbreak (simply do not install Cydia to avoid conflicts).
The step by step process is nearly identical to the rc9 release. A guide for Windows can be found here, and a Mac version will be up soon, so stay tuned!
Get the software here: