Directory Functionality Question

I want to set up a directory site where people can add content to specific pages within different categories. Ex. Books, Fiction, Add A Listing. I want the different pages to update themselves automatically when a person submits info to that specific page. I can create a basic form where people can add content, submit it, then I have to go in and essentially copy their content to the relevant section of the site. How do I automate the process? Get content input by registered site users to the specific pages? Essentially want functionality similar to Craigs List where someone posts to a very specific sub-spot and the content is added to that area without much moderation. Thanks for your time.