I am in the same exact boat. I graduated May 2011 in California and still haven't been able to find a job. I've been actively searching for a year now, but while I've been searching I've been volunteering at a free clinic and the American Red Cross to keep up my skills. This definitely has made a difference! I am so close to getting a job now, I feel it. I've applied to probably hundreds of jobs with 2 interviews and 1 interview coming up.
I recommend that you pick a couple hospitals and just focus on those. This is what I'm doing and it is so far working for me. I had 3 hospitals and realized that 1 totally wasn't going to work, so then I changed to a different one. I finally made a relationship with a nurse recruiter at one and he is trying to help me out. I did that AND I went in and saw managers face-to-face, it honestly makes the biggest difference. I used to be scared to snoop into hospitals and track down managers, but it really isn't as bad as you think it is (the nurses on the floor are nice and will help you). Also, network, network, network! Get the word out, have your family get the word out, talk to people! Even though networking is really hard to find a connection through, you can get one. I have been networking for maybe 6 months (with a lot of connections falling through) and my mom finally found a great connection for me last month!
In my personal opinion, cover letters haven't done anything for me except for waste my precious time. The only time I focus on a cover letter is when I get an interview. These nurse recruiters and managers are so busy that they barely have time to read that stuff when picking you out initially. Seeing someone face-to-face is the better way to do it, THEN work on the cover letter to bring to an interview. This has just been my experience though...
Maybe you should go find a volunteer RN position or look at working at a SNF to keep your skills up and to beef up your resume. I hesitated volunteering at first because I kept thinking, "what if I get hired...what if I have to leave them?" You can't think that way.
Anyways, I hope I gave you some helpful tips from a fellow new-grad
Good luck to you!