Add top level catlist to main menu?

[radianation]

I'd like to add the top level catlist of my site to the main menu. I'm using a modified Fruity theme and would like to have the categories listed underneath the regular menu on the left. How would I call this? This is supposedly so that the users can quickly bounce between categories when they are within an album several layers deep. If there is a better way I'm open to suggestions. Apparently the inline nav tree doesn't cut it for them. Thanks for your help.