We don't have a plugin to automatically export information, and aren't sure we'll be making one as there's quite a few ways to export info. We'd still recommend hooking up to another 3rd party component that can capture your data in a Joomla table and then export from there. With the plugin system that's in 3.1 now, though, you (or a developer) should be able to modify one of the existing plugins to export information as someone registers to whereever you want.
As for the blog extension, I'm not sure what you mean by filling in the new user information. We fill it in in Joomla, but not sure what fields in the blog component you'd want filled in. If you can give us some more information, that'd help us figure out a solution for you.
Searching for a nice blog with FBconnection
