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.
Futanari Dragon Queen 2
Futa...For Science! (A BBW Futa on Female Medical Exam Erotica): Book 2
Snowball Fantasies: Kinky Femdom Erotica
Queen Fanastasia's Wild Week: Day 1: It All Started Wth A Dragon
Release: Gender Swap Thrills (Gender Swap Erotica) (Gender Bender Thrills Book 1)
Transformed Into a Goth Girl Too (Transformed #16)
Transgender 3: He WAS My Ex-Girlfriend (f2m gender swap, gay erotica) (The Transgender Fantasy Series)
The Swap: A Sissy Transformation Story
Becoming Becky (Gender Swap Erotica)