Need help with my categories on the sidebar

Hi, I’v created a blog http://harukami.co.za/blog/ which is suppose to display categories that a grouped into two, the first category heading is Case Studies which should display categories and next to the category, the number of posts. The second heading called Other Links should be the same as the first heading but display different categories.

My problem is that I cant find a plugin that allows me to group or manage this categorie as I mentioned, Any idea or plugin that will allow me on how I should do it?