Gini Dietrich wrote something that I agree with wholeheartedly:
Blog Checklist #3: Use Strategic External Links
One of the things that drives me batty about media relations is the publications and bloggers who won’t include external links in their content.
They opt, instead, to link to all of their own content.
A study by Reboot found:
Outgoing relevant links to authoritative sites are considered in the algorithms and do have a positive impact on rankings.
Not to mention, most publications and blogs (unless it’s the New York Times) will notice that you’ve linked to them and will return the favor.
And, when you receive a link from a high domain authority site, your own search juice increases.
Just to amplify that point about getting links back from those you link to, it actually goes beyond that. Linking to people in your industry that you'd like to build a relationship with can be a great way to get your foot in the door, as I wrote in a blog post where I introduced a content creation and relationship building strategy I call Blog Riffing.