If you are running your own instance of WordPress on a host somewhere
you can download or update the plugin directly within your Plugins
admin panel.  You can also download the newest version here:
http://wordpress.org/extend/plugins/the-guardian-news-feed

Also, we posted instructions for using the plugin on the Open Platform
blog here:
http://www.guardian.co.uk/open-platform/news-feed-wordpress-plugin

UPDATE NOTICE:

The update (v0.4) to the Guardian News Feed plugin now gives you
control of your own title, tags and excerpts on Guardian articles that
you publish to your blog.  The plugin will seed those fields when you
choose an article to post, but the plugin will no longer overwrite any
changes you make to the headline and excerpt fields.

We moved the headline into the link at the top of the article to be
more clear about what the article is.

Of course, you can still add your own commentary at the beginning of
your posts above the horizontal line.

Lastly, we've made some improvements to the way the plugin behaves on
update for future releases.

Please keep the feedback coming.  We've heard people request images,
but we don't have redistribution rights sorted for that, yet.  We've
also heard people request some improvements to the search/browse
interface in the admin panel.  We can do that...ideas on specific
changes would be helpful.

Also, keep in mind that the plugin is open source and editable.
Obviously, we welcome any ideas you'd like to contribute.  If you do
make your own updates, please let everyone here know.

Thanks,
Matt