Originally posted by Parallax It depends on the lighting and how long you had the door open.
If you were under relatively indirect room lighting, opened the door and immediately shut it it's likely that some of the pictures toward the center of the roll will be useable.
If you were outside or took a second or two to realize something had gone terribly wrong you likely won't have anything useable.
The least risky thing, money wise, would be to have it developed but not printed.
I dev it myself, so at most I'll be out an hour and a bit of Rodinal... I think I'll dev it, I just didn't want to waste my time. It was outside, but in the shade, I just cracked the door open enough to see the film was across the shutter and closed it. This was with bulk rolled film...