al3x.de

User/File Management, downloadable files are session bound and .htaccess protected against hot-linking. 
Users are not wp users. Files are displayed in a jQuery powered filetree. 
Now with public download area, public downloads are not session bound. 
You can even tell wp which subdirectory of the public folder should be used as root-directory.

al3x_file_manager

A neat User/File Management with a jQuery frontend to display customizable directory/file tree. Now with public download area.

brechtryckaert

Limiting the cookie expire time of password protected posts. By default the cookie set when entering a password to access a password-protected post will be active for 10 days. This plugin turns this cookie into a session-based cookie. This means your visitor will need to re-enter the password if the browser was closed prior to revisiting the post.

Instant Cookie Expire

This plugin turns the cookie for a password-protected post into a session-based cookie.

al3x_file_manager vs Instant Cookie Expire