well artist gave essentially a un*x golf solution. I'll recast it and comment on a couple tricks.

first 'echo */' (or print) is a good way of getting directories if you are using a posix shell.

 
% echo dir*/ | xargs -n1 | sort -rnt- -k2,3 | perl -lne 'print if $. =
+=2'
[download]

the 'echo */ | xargs -n1' can be seen as a poor man's transpose. It is useful if you know your paths! spaces don't work directly ...and xargs understands some quoting

In the end it is safer to use:

% NL='
> '
% (IFS="$NL"; for i in dir*/; do echo $i; done) | 
> sort -rnt- -k2,3 | perl -lne 'print if $. ==2'


% steph@ape (/home/stephan/t) %
% cat dirdata                  
dir-100-1
dir-100-10
dir-100-2
dir-100-9
dir-100-99
dir-2-1
dir-28-1
dir-29-1
dir-29-2
dir-30-1
dir-3-1

% steph@ape (/home/stephan/t) %
% cat dirdata | sort -nt- -k2,3
dir-2-1
dir-3-1
dir-28-1
dir-29-1
dir-29-2
dir-30-1
dir-100-1
dir-100-10
dir-100-2
dir-100-9
dir-100-99

% steph@ape (/home/stephan/t) %
% cat dirdata | sort -rnt- -k2,3 | perl -lne 'print if $. == 2'
dir-100-9
[download]