The day has come (at least for windows users)! Here is the automatic jailbreak for 1.1.3.

Make sure you follow all of these steps carefully. Thanks to ipodtouchfans for this.

Download and extract this to any folder on your computer.
Run jailbreak.bat and everything should work on it’s own.
When the download of the firmware stops at 100%, don’t worry and don’t close the window, just be patient.

This requires you to be on Wi-Fi on jailbroken 1.1.2 with BSD Subsystem 1.5 or greater, and OpenSSH.
Also, be plugged into some kind of power source, like the Dev Team recommends in the README.

To get wiggles and home screen customization for free, add to your sources in Installer, then navigate to The iPhone 1.1.3 Apps. in categories and install “The iPhone 1.1.3 Apps”.
Don’t worry about patching Springboard or activation pop-ups, etc, it’s all fixed since this is the real iPod firmware.

Be aware, your applications may not show up, you’ll have to uninstall and reinstall them.
Some may not work at all on 1.1.3, but it’s the risk you take.

For an even easier way of jailbreak 1.1.3 check out this post.

Post any problems in the comments section.