BuddyPress.org

This is the plugin that I use for that: http://1uthavi.adadaa.com/ada-wpmu-sitewide-feed-plugin/

If you only have one blog (not MU) then you won’t need a plugin for this. When you go to subscribe to the feed in firefox (blue rss button on the right-hand-side of the address bar, you should see three options: one for the activity feed, one for blogposts RSS and one for blogposts Atom Feed. Another option I find useful is looking at the feed via Safari. I find that because Safari has it’s own RSS reader you can get an immediate look at the actual feed address by clicking on the RSS button at the right hand side of the address bar, where in firefox you are prompted to subscribe via a third party program ie: feedly, google reader etc.

I’d just create a custom page template and create a RSS feed from a filtered, BuddyPress activity loop that only outputs blog posts.

Here’s a guide that will help you create the custom RSS page template:
http://yoast.com/custom-rss-feeds-wordpress/

Here’s the activity loop codex page:
https://codex.buddypress.org/developer-docs/custom-buddypress-loops/the-activity-stream-loop/

*Set the action to “new_blog_post”