Smashwords
Smashwords is a self-publishing site. It is fairly popular, enjoying around 200 thousand active writers and readers to date. The site mainly focuses on novels (but it also accepts short stories and anthologies, so no worry!)
As most writers on Smashwords are young women, it is understandable that romance is by far the most prominent theme. Most of the published books here are not for free, though; they are marketed for a certain amount of fee. For those who are trying to sell their work, but not a keen fan of Amazon, then Smashwords would be an excellent alternative (not to mention that you do not have to pay anything in order for your work to be published, unlike Amazon).
Regarding prices, there are specific filters for both free and marketed stories. That way, free works still get enough exposure. According to recent statistics, almost half a million books have been published on Smashwords, with 80 thousands of them being free.
Website: https://www.smashwords.com/
Users: 200 thousand