getting posts from other site network in wordpress 3.0

hello, i have set up the new wordpress 3.0 with multisite network capabilities. What i want to do is get and show blogs from other network site in the main blog. Like if i have set up the blog at example.com and i have other network sites at articles.example.com, movies.example.com. I want to get the posts from the articles.example.com and movies.example.com to show up in the main site at example.com. Is there any parameter in query_post to get the post from different network sites?