The software only iPhone unlocking software from iPhoneSimFree is supposedly shipping this Tuesday reports Engadget.

iPhoneSimFree group announced their software only unlocking solution two weeks ago. Now they offer iPhone unlocking in bulk to wholesales only. Looks like they do not want to deal with end customer sales at this point. 50 licenses of their unlock solution sell for $36/each.
Unlocking is a two step process. First the an .app file needs to be installed on the iPhone. In a second step this application communicates with a server at iPhoneSimFree to register and the iPhone is unlocked.
There is no guarantee that the unlock withstands future iPhone firmware updates.
More details on Engadget and on the iPhoneSimFree site.