what you really seem to want is not some on-server script but an XMLRPC script that uses blogapi (.module)
I managed to post content to a sandbox Drupal with some hacked up Ruby script, using the very simple-to-use XMLRPC libraries: http://www.ruby-doc.org/stdlib/libdoc/xmlrpc/rdoc/index.html
Talking to your Drupal site is very simple with that library. and I am certain there is something like this for PHP (or any other language you like).
Bèr