RSS feeds are listing of headlines generated by web sites that you can read using feed readers like Google Reader and many others.
Here are the most commonly-used feeds for the Media Co-op network:
Media Co-op (entire network) featured posts
Vancouver Media Co-op featured posts
Halifax Media Co-op featured posts
Toronto Media Co-op featured posts
If you're looking for something more specific, you can find feeds on the profile pages of individual users, and on group pages. Just look for the feed icon: