The U.S. retailer WirelessImports if offering the software for $99.
Gizmodo recently verified that the iPhoneSimFree solution with a video of the unlock process.
The retailer you buy the unlock from will load the unlock software directly onto your phone, which will check to see if your IMEI is "allowed" to be unlocked. If it is, the software will unlock the phonea process which took us approximately 2 or 3 minutes, as you can see in the video.
Based on notes by the resellers, the software is actually not yet available so they are simply taking preorders.