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.
Dickgirl Diaries 1: Too Big, Too Thick - My Girlfriend Has Fourteen Inches (Futa on Female) (Transgender Erotic Romance) (Hardcore Extreme Erotica)
A Sissy Maids Life, A sissy maid missy series, part three (A sissy maid missy series, part five Book 1)
Transsexual Domination 1 - The Stalker Becomes the Sissy (Shemale Male Feminization)
Futa's Plaything (Futa on Female, Domination and Submission)
Coed Futanari (Futa on Female Transformation)
Pledging Tau Geta Delta - Part 1 - Dressing Up: An Erotic Transgender Transformation Adventure
Wrong Potion (A Gender Swap Story)
Switch: Before there was transgender, there was the story of Gary and Amber.
Unexpected Changes: An Erotic Transgender Transformation Adventure