You can filter the sales displayed based on the download count or by the percentage of reduction.
You can manage a "follow" list to be notified when a specific app is on sale.
To follow an app from the Play Store, use the "share" button and select "best app sale" to open the page of this app on best app sale. You will find the follow button and the price history.
You can also use the search function.
image : lh5.ggpht.com/GiCQ5s7O9DPCrHe4xmaXcXkb6owsMupeANE2lodYqQcQFy9RaH GcrIGlOlzwr1WEAOk=h400
You can download it here :
(or search "madri2" if you can't find it)