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.
Spring of Changes: Swapped for a Panty
Transgender Guide to the Universe: Science Fiction Gender Bender Romance Thriller
Sissy is Creamed: Five Transgender Body Swap Femdom Erotica Books
I'm Wearing My Wife's Panties: Dominated by Her Beautiful Boss (True Sex Stories)
Futanari Threeway ...for Science! (fff, futanari on female, MILF, older younger)
Office Femdom Erotica: To work for this ebony goddess, he has to prove he's willing follow any command (Interracial Femdom at the Office Book 1)
Pegged by My Boss: Chastity Device
He's the Perfect Woman: Gender Swap Revenge
Curse Of The Wereslut (Wereslut Book 1, Steamy Gender Swap Romance)
Having Fun In the Frat House Erotic Transsexual Story Tranny Erotic Story
Teen in Germany