Omni Secure Files is a plugin by omnilogic to create a back end secure area to upload and share files. perfect for a simple intranet file sharing site. supports large file uploads.
Can be configured to store files outside of your web root directory
Simple permission system based on roles
Supports uploading large files
Renaming folders and files
Short code embed tags
Download and info: http://wordpress.org/extend/plugins/omni-secure-files/