This is a website which is interesting and can give some unique information about things like sales ranks and if Amazon has tagged your book adult or not. There are a lot of little tricks you can use with this site, including finding out what Amazon bundles your book with or if they pair up your book with another for a discount.
I think it can be a useful tool to some so I am going to share the link. How you use it (or don't) is up to you.
Another really nice site, although not always accurate is this one. You can track your book sales and based on the ranking it guesstimates the number of sales in a month, or a week, or a day. You can load up any book sold on Amazon that you are interested in tracking.
All these sites have kind of cool stuff, and it might be distracting, but it is interesting. At least to me. Enjoy!