FileGator is a free, open-source PHP script for managing files and folders.
You can manage files inside your local repository folder (on your server's hard drive) or connect to other storage adaptes (see below).
FileGator has multi-user support so you can have admins and other users managing files with different access permissions, roles and home folders.
All basic file operations are supported: copy, move, rename, create, delete, zip, unzip, download, upload.
If allowed, users can download multiple files or folders at once.
File upload supports drag&drop, progress bar, pause and resume. Upload is chunked so you should be able to upload large files regardless of your server configuration.