XML-RPC posting?

Can WP support XML-RPC posting, like M*******T*** does? Cause it’d be really convenient to still be able to use my client (EspressoBlog on OS X, 10.3). If so, is it a plugin?
In either case, where is the XML-RPC server? I tried wp-admin/post.php, that didn’t work (not surprisingly, I was just grasping at straws)