There are 109 (if I counted correctly--a
big "if")
free Kindle mobi ebooks available from Kypros Press at the present time. I wasn't familiar with them before, but they seem to a publisher similar to Nisyros and Waxkeep.
Not all of the ebooks are non-fiction.
Follow
this link. The URL is for a sort from low to high, so if you want to just get the freebies, be sure that that you don't go into the next price point, which is $0.99.