I created for the website of my company a web page which is looking like a ftp, but more comfortable. I’ve even included it within the wordpress site. Sorry to not be able to show it you, because it’s in the company’s network, but imagine a wordpress homepage and when you click on “Documents” on the left side, it will open in the central frame the content of a Web-Ftp, you can browse in folders and when you click on a file, it will open it, or you can force them to download it by clicking on the document.

Please have a look at this great PHP file: http://autoindex.sourceforge.net/

AutoIndex is a PHP script that makes a table that lists the files in a directory, and lets users access the files and subdirectories. It includes searching, icons for each file type, an admin panel, uploads, access logging, file descriptions, and more.