Building a fan base for your business on social media outlets such as Facebook, Twitter, and YouTube can get you higher visibility, increased website traffic, and more business. Using social media as a marketing platform goes hand in hand with SEO as far as driving more traffic to your site.

For example, you might use Facebook to survey customers about their experience with your company or ask them to offer ideas for new and improved products (especially effective if you offer a high-value incentive). With the immediacy of Twitter you can announce new products, last-minute deals, contests, or special offers. Social media sites can also be a place to network with other business owners and share ideas. The broad base of these sites can get you viewed (and shared) by thousands in a very short time, which can translate to lots of website traffic.
Take social media seriously and optimize it for better rankings, just as you do your website. For a good roadmap on how to get started using social media to boost rankings, check out this 2009 Mashable article by Lee Odden:
http://mashable.com/2009/04/15/social-media-seo/