iBrickr makes iPhone 1.1.1 Downgrade Easy
If you want to downgrade the firmware on your iPhone, iBrickr has an easy option for downgrading the firmware from 1.1.1 to 1.0.2. Thus spoke Nate True:
Just a small update - if you want to downgrade your iPhone from 1.1.1 back to 1.0.2, iBrickr will guide you through it. No button holding either, it's easy!
And if you'd like to download it, iBrickr has its own web domain that will redirect you to the proper place. The update doesn't work with unlocked iPhones that were bricked by upgrading to 1.1.1, but that tool is still on the way from possibly multiple sources.