To whom do you address your resume and cover letter, when you don't know the name of the person?

When you don't know the name of the actual person to whom you're addressing a cover letter or resume, see what you can find out via LinkedIn or your network. Failing that, go with "Recruiting Manager". It will be tough to know what to do when working with staffing agencies.

When applying online to jobs posted by agencies, you'll want to address your letter to the agency. When you make contact to someone at the agency, let them know you can write a letter for each opportunity for which your materials are submitted if they feel it would be helpful. A good agency recruiter acts as your cover letter - talking up your strong points and emphasizing goodness of fit.