Looking a Deeper Category Structure

Pardon me if this is a dumb question or somehow I missed this in the Admin interface....

I wanted to know if there is a MOD out there (Or this feature is there and I'm missing it) that would allow a deeper category stucture that would allow more specfic discussions i.e.

WWW Technologies
          |_____HTML
          |_____ASP
           |        |____ASP Classic--> Thread Topic
           |        |____ASP.NET--> Thread Topic
          |_____Flash
          |_____etc.

Thank you for your thoughts, a fantastic product!
I liked it so much I even registered it!