I’m the Director of Staffing for a $500+ million company (shameless plug) and the reality is that it doesn’t matter who you address the cover letter to. Unless you put something rude or annoying (e.g., ‘Dear HR weenie’, or ‘Dear Hiring Nazi’) we don’t care. Most of the big companies are scanning resumes into large computerized databases that work on a key work search engine, so cover letters, and other stuff is tossed. Or even if they don’t use scanning technology, very few people read the cover letters anymore, except to look for gramatical or spelling error. We simply turn the page to the resume and check out the KSAC’s (knowledges, skills, abilities and competencies.
My advice, screw the “parachute” books (which are the laughing stock of professional-HR types) and get a recently-published ‘resume advice-type book’ that will help you ‘beef up’ your resume, and during the selection process show some basic business common sense and consideration (i.e., follow up calls, thank you letters…)