Every Friday I take the initiative to search through thew newly free titles on Amazon, and to identify those that might be of interest to trans* readers, fans, and lovers. Even if you don't have a Kindle, you can still download the titles through one of Amazon's free reading applications, and covert it (if need be) with Calibre. I can tell you I do most of my reading on my iPad, using Kindle for iPad, and it works beautifully.
Please do be sure to check the price before downloading anything, though, as most freebies are limited time offers, and some are specific to certain regions.
Gender Bender in the Club
Her Sexy Surprise
Strange Strong Women
Gender Clones Volume 1 (Dystopia Science Fiction Erotica)
Butt Slap (mm, mmm, mmmm, crossdressing, prison, sissy)
Planet of the Futas (Taboo Futa on Female Menage Gender Bender Sci-Fi Erotica)
Peaches (A Futa on Female Transformation Erotica)
The Cougar's Pegging Revenge (Dominant MILF Erotica)
Sentenced to Gender Swap: Gay Nurse Caught
The Blue Vial: A Gender Swap Fantasy Short Story