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.

 
Features:

• You don't have to put index.php in every subfolder - it automatically lets you access subdirectories
• Shows different icons for each file type - includes three different icon styles
• Ability to hide/block certain files, folders, or file extensions
• Works on all servers that support PHP 4.1.0 or higher (including PHP 5)
• No databases needed
• Ability to upload files and to have user accounts
• Built-in admin tools (available when logged in with an admin level account)
  • Creating and deleting directories
  • Uploading, renaming, copying, and deleting files
  • Log viewer and visitor statistics
• Searching for specific files/folders
• Access logging and statistics (stores user's IP in a text file along with the time and file request)
• Anti-Leech feature
• Bandwidth limiting
• Files/folders can have custom descriptions
• Thumbnails of images can be generated and displayed
• Can keep track of number of downloads for each file
• Nicer looking than server's default output, and the display is customizable
• Version 2.0 uses a template system for easy customization of HTML output
• Available in 35 languages
• XHTML 1.1 and CSS compliant, so it displays correctly in all browsers
• This software is free

See the demo on this site to get an idea of how it works!