A recent NY Times "Career Couch" article has some great advice on making the best of being unemployed while searching for a new job. I want to expand on some of the key points a little bit.
-Remembering you do still have something to offer - this could be your insight on changes in the industry or your take on an industry-related article. Sharing information on LinkedIn is a really easy, no-pressure way to keep your name in the minds of your connections, but sending an article to someone who you think would be genuinely interested is a great way to make a bit more of a personal connection.
-Staying active in a consulting, part-time, or volunteer capacity within your industry is also really important -- not just because it keeps you busy and helps fill in gaps on your resume, but because it keeps you plugged in and offers a natural way to continue expanding your network.
-It's also key to remember that while you want to be honest about your current employment status and reasons for leaving your last position, you don't want to come across as being too desperate. Employers are (understandably) wary of hiring someone who is just looking for any job - they want to hire someone who really wants their particular job. If you're giving off a "I just need a job" vibe, you might scare off an employer who is concerned you'll end up jumping ship for a better job when it comes along.