How to: Minimize link categories?

I’m wondering if there is a way (plugin, code, theme whatever) to minimise links to link categories on the sidebar in wordpress, so that link categories would be displayed, and clicking on a link category would open a submenu displaying that categories links?

Ideally what I’d like to do is have my site’s sidebar (http://dbspin.com) initially display the links in only one category ‘Navigate’, and allow the display of links in other categories ‘Offsite’, ‘Blogroll’ etc, only when a user clicks on the link category itself.

E.g.:

Link Cat 1 (links visible)
– Link 1
– Link 2
– Link 3
Link Cat 2 (links hidden)
Link Cat 3 (links hidden)

Cheers!