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.
Whispers of Change
And Sissy Makes Three: Femdom Menage a Trois Erotica
Confessions of a Secret Dominatrix
Pool Shark and Other Femdom Stories
Stranger Sex Swap (Gender Swap Sex Change Erotica)
Bewitched and Switched (Reluctant Gender Transformation Mind Control Erotica)
Big Top Gender Swap
Futa Angel Fun Times (Mind Control, Futanari, Paranormal Erotica): (Guy Taken By a Futanari Angel)
Serious Side effects (a gender swap story)
Hip Hop Gender Swap (Becoming a Thug Wife Book 1)
True F@#*ing Stories. Volume 1
Crazy Bitch (Bitches and Queens Book 2)