Good category menus?

Hi,

I’m building a travel newsletter site for a client, and I’ve set it up so that every newsletter is a blog post. I’ve been looking around for menus to use in the sidebar, specifically aimed at showing blog categories and subcategories (not pages). Every country is a category, and under Japan for excample, you’ll find a bucnh of travel blog posts for each destination in Japan. I’m looking for a menu plugin I can use in the sidebar, preferably where the blogposts under each category will expand into a submeny when I hover over the category itself (not below, but in a menu to the side of the category menu).

If you want to check out the site to get a clearer picture you can go to http://jorund.spreeluxe.com/destinations/ . I already have a decent menu there, but the problem is that it expands below the category, which causes all the other categories to be pushed around. It would be great if you could reccomemend any good plugins like this (free or paid options).

Cheers =)