[Why would the Huffington Post put a huge list of competitor news sites on the bottom of the homepage? It goes against everything that I know about SEO. They’re very focused on SEO and organic placement. They wouldn’t do this unless it helped (or at least didn’t hurt) SEO.]
It helps to provide useful content, including links to relevant external websites, this improves your user’s experience. Google uses this very principle to great benefit on their own websites.
The concept is well known in SEO as building a hub site.
It generally translates into high SERP rankings.