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.
Becoming a Thug Wife: Complete Series (Interracial Gender Swap Erotica Book 1)
FutAir: Flight 1 (A Futa on Female Erotica): Episode 1
The Futanari and The Billionaire (What the Futanari? Book 4)
Swapped by the Futanari Djinn (Gender Change, Paranormal Erotica)
Hocus Pocus Gender Swapicus: Girlfriend (Gender Swap, Succubus, Transformation Erotica): (Part 2)
Bimbo Akimbo: Innocent Girl Gender Swapped and Becomes a Sex-Crazed Slut (Kindred Embers Book 2)
Hocus Pocus Gender Swapicus: Professor (Gender Swap, Teacher, Succubus, Transformation Erotica): (Part 3)
My New Life as a Girl (Transgender Erotica, Spanking, Submissive)
Transformed Into a Bimbo (Transformed #9)