How can I find advertisers for my Web page?

I have a web site related to the athletic shoe industry, but I do not sell shoes or anything else. It's an online newsletter, which was subscription based. However, I'm exploring the possibility of trying to earn revenue through advertising and offering my service for free. So I'm trying to find out how to find advertisers who would be interested in using my site, to see if I could make it profitable solely through ads. I can pretty much guarantee 1000's of readers a day from all the major shoe companies.