Volunteering can be a great way to get some experience when you're first getting started in a field. However, you should volunteer for a nonprofit. You can't volunteer for a for-profit company.
Asking a company if you can do free work for them tells that company that you believe they will violate federal law to take advantage of you. You're not doing them a favor. You're asking them to do an enormous amount of work by having an attorney help them create an unpaid internship program just for you.
First hand experience from someone who has used multiple different sites and techniques to find freelance clients. I think the cold contacts really only works because she put in so much effort researching and targeting specific companies with customized messages; I doubt generic cold contacts would have done as much for her. Super fan-girling over here that @ChristyATucker linked to some of my posts! EEE! - Where to Find Freelance ID Gigs http://t.co/34hyGXDHz2