There's also the 'Original, Uncut Version', which is an hour and a half longer than the Director's Cut. That's my favorite.
http://www.amazon.com/Das-Boot-Origi...words=das+boot
There's also the special Blu-Ray set, which comes with the Director's Cut
and the original Theatrical Release, which is an hour shorter.
http://www.amazon.com/Das-Boot-Two-D...words=das+boot