"To Whom It May Concern" would be my generic recommendation.
(although my original typo "To Whom I May Concern" might actually be an attention getter
I've received "Dear Sir/Madam" previously.
The combination of "Dear" with a generic salutation comes across as disingenuous to me.
If you can determine the first considering level of contact. E.g., name(s) obtained through Human Resources, use the name of a person(s) likely to first act on your letter. Address it to that individual. If there is more than one possibility, send multiple letters.
This post was edited on 12/10 at 8:15 pm