Joomla! includes a variety of modules that can be used right away. One of them is the Section module. This module shows a list of all sections that have been created in Joomla!. But sometimes it is more usefull to have a list of all categories within a section.
At this point the default Joomla! modules cannot deliver what you want. We took the section module and changed the code so that you can select a section and their categories will be shown as a list. To see the module in action take a look at "Article categories" on the right side.
You can choose to display the results either as a table like the section module or as blog layout (what the section module does not offer).
As a small addition we included the option to select from 3 different styles. If the delivered styles do not fit your needs you can edit the css-files: ~/modules/mod_categories/style1.css for example.