"Mastheads.org is a collaborative directory of 200+ magazine mastheads
built for professional writers, editors, illustrators, photographers, designers, researchers, and media mavens. We list the full staff as they are listed in the magazine, with mailing addresses, phone, fax, and e-mail formats." However, you might not want to use it as your absolute Bible, as it's not constantly updated--continue to talk with your fellow freelancers and check other references like Masthead Online and the Revolving Door. But it's a useful resource nonetheless.