I have finally rewritten my File-center project. It is a simple interface to download and upload files. Now I use Smarty for this project and the default template is really nice. The scripts for download and upload are simple too, and you never need to get to another interface. You just upload a file, and next it appears in the current working directory. If you want to download a file, the page will be reloaded and the download will start within 3 seconds.
It is on Freshmeat.net/projects/filecenter/ but the webpage of the project is hosted on my french homepage.