Transfer post from one blog to another?

Ok - so assume Site A has all of the posts on it and Site B needs those posts on it too (duplicating content isn't a great idea).

You should run a cron job on Site B that runs a function and checks the RSS feed from Site A and imports the content.

You can use fetch_feed() - http://codex.wordpress.org/Function_Reference/fetch_feed in order to parse the XML and then you can use wp_insert_post() http://codex.wordpress.org/Function_Reference/wp_insert_post to add them to Site B.

You can then run this cron job every 15 minutes so Site B takes a copy of the posts from Site A.