A blog should be considered the central hub of your social networking universe. Everything you do should drive traffic back to your blog, or website, as a way of combining all your efforts to give your brand maximum exposure.
Once thing you can do to help populate your social networks would be to update your status with your blog posts when new content is published.
By no means is auto-populating a service like Twitter going to get good results on its own, but as one piece of a social networking strategy, it can help a network grow.
Here are just a few of the many ways you can automatically syndicate a blog post to social networks.