WordPress.org

For posts, any links to local media (images, documents, etc.) will automatically have the file type and size appended in parentheses, so visitors to your blog will know what they're about to download when they click links to media.

Notes:

• Requires PHP 5+
• Only applies for full posts, not comments or post excerpts.
• Specifically only works for media files uploaded using WordPress' media upload function (i.e. files in the wp-uploads directory).
• Parses every post through DOMDocument on view, so unlikely to be wildly efficient.
• Link parsing might be a bit rough - needs more extensive testing.
• Invokes the 'file' program to figure out file types, which gives very pretty and accurate output, but again probably isn't very efficient.