Your last point about claiming to not know the password is interesting... If I had a mustache I'd be stroking it by now. ;)
I ended up writing a simple shell script using sha256sum and dicing it several ways, a GUI app seemed a bit clunky for me.
read -s p
hash=`echo -n $p | sha256sum | sed -e 's/-//' | sed -e 's/ //'`
echo '64: '$hash
echo '40: '${hash:0:40}
echo '20: '${hash:0:20}
echo '16: '${hash:0:16}
echo '12: '${hash:0:12}
echo '10: '${hash:0:10}
echo '08: '${hash:0:8}
Edit: One other neat thing about this approach is that you can honestly say that you don't know what the password is (if you are ever asked). You know how to create it, but you have no idea what it is. That may matter in some situations.