So I do like to feature resources that have helped me succeed as a designer and a business owner. Most professionals I've met over the age of 30 are weary of online networking sites. They might think of Myspace or Facebook (which aren't bad places to network either, if you know how to use them).
But LinkedIn is very different. First of all, is a professional-only networking site. It's a place to post your resume, job experience and what kind of business connections you're looking for.
Second of all, it's a great place to ask for testimonials. Your "friends" on LinkedIn can write ones about you, and they can ask you to write one about them. The more people who recommend you, the higher your name will appear in a LinkedIn search.
Lastly, I will look at my friend's connections. If they are connected to someone I'd like to meet, I can simply ask my friend for an introduction. I have met many new people through LinkedIn, some of which has led to new business for CurlyRed.
So don't knock it till you've tried it. Oh, and ask me to be your friend if we aren't connected already.