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.
The Games - Parts One to Four (A Tale of Forced Feminization) (The Manhood Games Series)
Stella Book 1: Female domination erotica only for broadminded adults
The Sissy Humiliation Bundle + One Bonus Hotwife Swapping Story!: 10 HOT SISSY SCENES, NO PLOT!
Pemberley Unbound 2: The Prettiest Stable Boy
Transformed into the Office Slut (Gender Transformation Erotica)
Sexy Science! 3 Stories of Paranormal Ménage!
The Pop Star's Big Secret: The World's Most Famous Singer is Really a Futa
The Bully (The Omar Bell Universe Book 1)
From construction guy to pop princess
Men and Their Toys Pink Edition: 6 Unbelievably Erotic Stories (bondage, domination, paranormal, gender swap, toys, & more!)
Futanari Sex Ranch (Futanari Femdom Erotica)