Publishing to multiple WordPress installs

I’m sure this is likely to be a subject covered before, but is there any simple method or technique for having WordPress publish a given article to multiple sites (i.e. multiple databases)? I understand I could quite easily have WordPress-published articles appear on multiple sites hosted on the same webserver (or indeed, on different webservers by connecting to a given database server) but what if (for instance, for security reasons) non-localhost database connectivity wasn’t possible?
I imagine I could stumble through the WP code and effectively duplicate the insertion process, but this may be a rather ugly hack, and could have implications I’m unaware of. Has anyone else tried this who has tips for how best to implement this kind of system?