Apparently there are two solutions-- the one above is part of a script based on ieraser, and the other is called iUnlock (Engadget says that one "appears to be in a more complete state"). We aren't yet sure what these do-- whether they're an actual unlock, or simply a reverse engineer of the iPhoneSIMfree unlock released the other day.
Either way, it doesn't much matter (hope iPhoneSIMfree made their money while they could). Even if these solutions (both of which seem to be straight code at this point-- there's still no simple "userfriendly, automated tool" available) aren't exactly what people need to use any SIM in their iPhone, a free, open source solution is likely just around the corner. Until Apple changes the firmware, that is.