I'm trying to move back to WP for our blog, after struggling with a clunky CMS for a few years, but we'll be sticking with that CMS for the rest of the site. Is there a plugin (or code) that I can use to pull the recent posts in a particular category from my WP blog to the sidebar of my non-WP site? Assume full permissions on both the WP blog and the external site.
The easy way is to just use a PHP based reader and parse/output the results. Maybe your CMS already has one but if not and it's based on PHP you can use,
Then you simple point it to your categories /feed, like -->
You can easily customize a feed to show whatever you want http://codex.wordpress.org/Customizing_Feeds
That way you can have a feed that only shows recent posts from one category using WP Query, you just have to point your reader to it.
Alternatives you can try via a plugin that allow for external HTTP requests: