When I was a Recruiter I worked with many candidates who went through the industry mini-recessions of 1991 and 2001, and they faced the same problems you may be now -- filling those gaps between last full-time employment date and present day. From experience, I can say nearly all potential employers will understand if you haven't had a full-time job lately -- we've all been part of this ugly recession -- but that doesn't mean you can or should ride on the recession excuse alone. There are tactful and yes, truthful ways to explain your lack of full-time industry work during this period on your résumé and help you stay competitive.
The best way I've seen to present this period is to label yourself a Contractor/Consultant, with clients who relied on you to perform services similar to the type of full-time work you seek. (Before you moan that there were no opportunities to keep you working in the industry in some capacity, did you think of volunteering with a non-profit in their marketing/media department or finding a friend, family member, or neighbor who has a small business you could help? If not, try these routes.) You would be well served to also purchase a domain with your name or consultancy name in it, and set up an e-mail account so that can be used with your contact information in the résumé header.
Or if you have found yourself with multiple short-stints that will take up too much real estate on your résumé to list individually (remember the one-page rule until you're in management), you may want to consider a catchall entry for the time period. For example, “January 2009 - Present, Performed various services including SEO management, database marketing, Web site copy review, and genearal marketing consultation for X Corp, Y Corp, Z Corp, and Company B.” You can then include any clients you worked with, Web site urls from digital projects if relevant, and specific accomplishments for the companies you freelanced for. Basically, treat all your small assignments as one traditional employment entry on your résumé. This will also help the overall look/format of your résumé.
And finally, if you really haven't done anything in the professional realm, hopefully you've kept yourself occupied with some noble personal causes. Many potential employers may like to see this, too. For example, if you became a Substitute or Teacher Assistant at your child's school, would be seen as a productive way to ride out the recession. Similarly, if you pursued an interest in the arts or philanthropy, those areas should show you in a positive light.
If you've been playing around on Twitter and Facebook for six months, though, it's time to get with the program and take some initiative because employers are looking at résumés again, and you need yours looking good. It's never too late to get out there and find something that shows you are still part of the industry and up on the latest and greatest. But I do suggest you start now as we've seen a nearly 100 percent increase in new job listings this quarter over the last three months of 2009.
Good luck and happy hunting.