Apple has posted the download links to the iPhone 1.1.2 firmware, for direct downloading:

iPhone1,1_1.1.2_3B48b_Restore.ipsw

iTunes has yet to reflect the new firmware, but some adventurous souls have downloaded the link manually to upgrade their iPhone.

- Modem firmware: 04.02.13_G
- TIFF Exploit patched (per Engadget) so JailBreakMe no longer works
- Devices in iTunes, battery icon shows up to indicate it charges.
- Slide for emergency call changes languages
- International keyboard available
- No horizontal text messaging (per villanova329)
- iToner works.
- Screenshots of 1.1.2 from MacNN
- Custom Ringtones section