Today appears to be the day that I receive resumes from a wormhole opening into the first half of the Twentieth Century. Along with the Mrs. mentioned previously, I just received a resume that starts out addressing me and my counterparts as "Gentlemen."
Okay, it's 2007, and unless you are posting a memo above a urinal, it's no longer really safe to address any business correspondence to only "Gentlemen."
Before the Contrary Maries and Misters start waxing red-faced about political correctness, it's not about that. It's just a question of ACCURACY.
Especially with a resume, because if my experience is any indicator, Human Resources is like 90% ladies. Sometimes I get a sinus headache from all the estrogen.
ANYWAY. Just say like "Hiring Manager:" or "To Whom It May Concern" or whatever. I don't care. Just don't call me Mister. I had a short haircut when I was a kid and somebody called me "Young Man " once and the wound still smarts.