As of today there are 2 hacks available on the net for the iPhone 1.1.1 firmware :

1. TIFF Exploit : Basically, opening a carefully crafted TIFF image will crash mobile safari, causing a buffer overflow and allow for arbitrary code execution. This same exploit was used more than 1.5 years ago to crack the PSP firmware.
2. iPhuc method : This hack gives access to full directory with read / write access but still some  paths don’t have write access.

But till now these method can’t unlock the iPhone,so you are better of using the 1.0.2 firmware.
Google for more detailed info results