How to find free AZW, MOBI, PRC eBooks on Amazon Kindle Store

Amazon Kindle Store offers free ebooks from public domain. Also Kindle Store offers some ebooks for free for a limited time.

Note that most ebooks in the Kindle Store are free for US residents only. Of course you can change the country in your account to the United States, but Amazon checks your IP address, so you need to use a US IP address to get free ebooks without any limitation.

How to find free ebooks in the Kindle Store

Big Deals
This is more of an official listing of Kindle books that are currently available for free download on Amazon to Kindle users.
You should also check the Bestsellers category on Kindle Store as it lists free titles as well.
Sort by Price
When you search for a Kindle book (or any other item) on Amazon, it displays search results by relevance.
If you change this default sort order from "Relevance" to "Price: Low to High", you'll get a list of all Kindle books that match your search keywords and are available for free download.
Listmania
Listmania Lists are basically a list of products compiled by Amazon users. You can use search phrases like "free kindle books", "kindle freebie", "penny kindle book", etc. to discover lists that may free books you are looking for. Just click onto the "kindle freebie" and you will find plenty of free ebooks.

Note that even free ebook from Kindle Store are protected by DRM. If you want to read such books on Sony Reader, Nook, iPad or any other eBook Reader, you need to remove DRM from .AZW files.

You don't need to be a hacker to crack the encryption of DRM protected AZW files. Just download freeware ebook DRM removal tools archive including DRM removal tools for ePub files. And try to use a Calibre plug-in first.