The best way to get me to unsubscribe from a mailing list? Start bombarding me with holiday specials, "last minute" holiday specials, "last chance" holiday specials, etc. I might love to get an occasional email, or at least not be overly irritated by it, and it does keep your site in front of my mind, but an email a day? Annoying. I've unsubscribed from three in the last few days, lists that I don't mind receiving, in fact, kind of liked getting, until they got on my last nerve this week.