LinkedIn.Com

Okay, admit it, your facebook isn't a networking tool. Just because you have your work history listed within your personal profile, doesn't mean you're networking for jobs or promoting your business.

Myspace, twitter, and facebook, are great for social networking, but I recommend LinkedIn.com; especially for anyone looking to network with other small businesses.
As time goes on, net savvy employers as well as private enterprises will link up on sites like this.

As far as SEO and real networking is concerned, it always helps to have a site that functions like a social networking site, but is really geared toward professionals and small businesses. It also helps to have an outlet to add hyperlinks and connect your website to the world, even if it's just a small blog.