renanivo

Adds some Multisite-specific functions to WordPress’ XML-RPC interface (http://yourdomain.com/xmlrpc.php).
Using this plugin, you can create a blog, update the archived status and get a blog ID using a remote software (another server, a desktop software, a mobile software…)
The functions enabled by this plugin are:
<ul>
<li>Create Blog (ms.CreateBlog)</li>
<li>Get Blog Id (ms.GetBlogId)</li>
<li>Update Archived (ms.UpdateArchived)</li>
</ul>
refer to the <a href="http://wiki.github.com/renanivo/WP-Multisite-XML-RPC/" rel="nofollow ugc">wiki</a> for further documentation

Multisite XML-RPC

Adds some Multisite-specific functions to WordPress' XML-RPC interface.

confuzzledduck

Syndicate Out syndicates all posts made in a specified category (or optionally all posts) to any other WordPress 
blog(s) in real time. This enables blog owners to create automatic aggregating, or topic specific blogs from any 
number of different blog sources without relying on RSS feeds or any kind of timed events. Put simply: it re-posts 
the content of one blog to one or more other blogs.
The plugin uses WordPress’ built in XML-RPC functionality to push posts to the target blog. XML-RPC will need 
to be enabled on the receiving blog in order for this plugin to work. For versions of WordPress 3.5 and later 
the XML-RPC is enabled by default. For versions prior to 3.5 it will need enabling in the admin panel.
For versions 0.8 and higher of the plugin the sending blog needs to be WordPress 3.1 or higher due to the use of 
the WordPress enhanced IXR client, and the receiving blog needs to be WordPress 3.4 or higher so that the XML-RPC 
WordPress API posts functionality is available.
More information is available, feature requests and bug reports are gladly accepted over on the 
<a href="http://www.flutt.co.uk/development/wordpress-plugins/syndicate-out/" rel="nofollow ugc">project’s own blog</a>.

Syndicate Out

Syndicates posts made in any specified category to another WP blog using WordPress' built in XML-RPC functionality.

Multisite XML-RPC vs Syndicate Out