Once you book is up on Amazon there is a temptation to keep checking that sales rank. I was an early adopter of Titlez, which still works but seems fairly neglected. There are not recent updates to the sites which is a pity as it might also have been a useful publishing news source.
Now there are other services that will track your ranks for you including Charteous and Sales Rank Express. The latter offers a real time widget for your site, but a word to the wise--it is not good marketing to post this if your rank is not good! Anything greater than #50,000 suggests less than a sale per week, and the cany Amazon customer knows this and might be put off.
If you are using any of these services please let me know what you think of them.