Here are some answers to frequently asked job application / cover letter questions:
How long should the cover letter be?
Do not exceed one page. Don't crowd - make sure there is plenty of white space on the page.
Who should I address the letter to?
Ideally you should get the actual the name of the hiring manager and address the letter to that person. Try to find out the name by looking at the job ad or on the company webpage or by telephoning and asking who the recruiter is. If you cannot find a name, then use a more generic term like 'Attn: Hiring Manager'.