I updated the list_casts function on my website (www.chait.net) to support the sliding-doors button technique. Just download the wp-includes/template-functions.php file and look at it (or whatever that darn file is…).
Basically, I added the ability to pass in $before and $after instead of them being just locally-defined variables. This way, I can add a span or a div around each of the links.
However, you could also use #menu ul li { rule } to add borders. Well, more specifically, you’d want to add a div id=’catslist’ or id the ul around the call to list_cats, then do #menu ul .catslist li {rule}. That rule could add a border around each of the sub list elements. Actually, just to confuse you, it is probably:
#menu ul li .catslist ul li
Or something like that. You can obviously simplify the rule down to:
.catslist li
… most likely (I’m still learning the particular language issues with referential style overloads…).
In theory, you could do it just adding a unique id to the ul for the cats list. Or you can go way overly complex (like I did) with divs and spans and excess markup… I’m into excess markup! ??
=d