How does one programmatically manage posts from a external php script?

You can remotely create posts programmatically via XML-RPC

e.g. PHP

http://www.nickycakes.com/post-to-wordpress-remotely-with-xmlrpc-in-php/

Java

http://code.google.com/p/wordpress-java/

Of note, the media library handles image EXIF data etc, it might be more convenient to switch from using posts to just displaying the latest uploaded attachments that do not have a parent post (attachments with a parent post are attached to a post or in a gallery)