Run this inside an empty SVN checkout (e.g. svn co -N <repository>) and it will sparsely check out the entire sub-tree of directories (excluding files). Unfortunately, in my environment Subversion only checks out at about 100 dirs/minute so it's not very

sparse_checkout.pl

sub do_dir {
  my ($dir) = @_;

  chdir $dir;
  my @entries = map { chomp; $_ } grep { m{/$}xms } qx/svn ls/;

  system qw/svn update -N --set-depth=empty/, @entries;
  do_dir("$dir/$_") for @entries;
}

do_dir($ENV{PWD});