There are many books on Amazon.com that are always free, and there are many sites dedicated to free eBooks whose owners search Amazon.com and list these always-free eBooks to help
Source: 16 limited-time-only free eBooks for the Amazon Kindle for 13 September 2013
Source:
http://82s.net/news/u-s-national-news/16-limited-time-only-free-ebooks-for-the-amazon-kindle-for-13-september-2013/