The iPhone elite development claims that they have managed to jailbreak the iPhone 1.1.2 firmware. Keep in mind that this hack is completely unproven at this point, so you may want to wait for some other poor bastards to screw up before you try it. [Elite Download via Tuaw]
Update: Thankfully, Ibrahim clarifies in the comments, because I'm not sure I understand myself. The team has basically figured out a way to downgrade 1.1.2 to 1.0.2 or 1.1.1 and unlock it. They haven't actually unlocked the 1.1.2 iPhone, because it hasn't been jailbroken yet, but they have unlocked the new modem firmware.