When 1.1.4 was released, many were surprised to hear the good news that they could still jailbreak their iPhone on 1.1.4 using ZiPhone designed for 1.1.3 and earlier. The bad news was that the activation and unlock capabilities of ZiPhone were not effective on 1.1.4 and even jailbreaking 1.1.4 sometimes was unpredictable. All of these concerns are now a thing of the past, thanks to the release of ZiPhone 2.5.
ZiPhone 2.5 features a GUI interface which can be utilized to perform any or all of the following functions: jailbreak, unlock, activation. After jailbreaking, ZiPhone will place Installer.app on your iPhone which will give you an OTA (over the air) method of installing other applications directly from the iPhone. Alternatively, you can use SSH or other third party tools to install applications (though Installer is recommended).
The author of ZiPhone is currently recommending that those who wish to update their iPhones to jailbroken 1.1.4 perform a restore/update to 1.1.4 instead of an upgrade from 1.1.3. This is reportedly due to inconsistencies with Installer.app which will likely eventually be remedied by the creators of Installer.app, Nullriver Software.As with previous versions of ZiPhone, ZiPhone 2.5 can be used to jailbreak, activate, or unlock any version of iPhone firmware.
ZiPhone versions are available for both Windows and Mac OS X, and can be downloaded here.