This Site has Info on Online Bookstore Rankings
Marketing Through Amazon - Tentacle Tips (GreenTentacles)
I would have to guess that the Catholic Digest piece has greatly increased the sales of my book on the Mass. For today it has jumped up to around 2,000 on Amazon and I think is still around 1,000 on Barnes and Nobles. From what I can determine if you are in the top 10,000 in sales the rank is updated hourly.