This hack allows you to attach categories and forums to a higher level category or forum or to the root index, giving you the popular sub forum capabilities. It also gives you the ability to create a forum link (links displayed as forums), set a picture for each forum or category on the index, keep the unread flag to the message even after closing the browser and much more.
It comes with a wide range of display options that you can setup in the ACP as well as various other parameters. You can also allow users to set their own display preferences.
This download is the full hack code installation. A package of pre-hacked files
is also available.