Taking a page from the Apple iBooks store, Amazon has finally created a separate list for the top 100 free ebooks so that they no longer clog up the top 100 Bestseller ebooks list. Take a look at the new layout for the Bestsellers in Kindle store lists.
The top 100 free and paid lists also extends to the some of the various genres. So if you look up science fiction or mystery you can see the top paid and free ebooks in separate lists for that category. It makes browsing through ebooks much easier. Now if Amazon would just add some more sorting and filtering options . . .