I found this mobile site works well with my kindle reader and my kindle ebook reader app.
For mobile, you may need to add “/?m=1” to show the mobile friendly site.
The site categorizes kindle ebooks and sort them by price from low to high. All $0 books appear on top of the list. In some categories, like Business and Investing, there is hardly any free ebooks. But for most of them, there are hundreds, even thousands, of free ebooks in each category.
I like using it in with iPhone. Press the “buy” button and the ebook will download to my phone’s kindle reader app. At the same time, it is transferred to the kindle reader as an archive.
Amazon is selling most of its ebooks at higher price than their printed version. I take this free ebook list as a compensation to people like me buying quite a number of ebooks from amazon.
<2013 Jan 26>
I extracted the urls and put them here. It is mobile friendly.