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.
Straight Boy/Queer Girl: a Memoir
Nowhere to Hide (crossdressing, threesome)
Transgender: Help Your Transgender Teen - Grieve, Transition and Support Change
Futanari Next Door (Futa Transformation Futa on Female)
Inked and Bared
Creamy Drink (Futa Dairy Gym 1)(Futa-on-female, Hucow, Exhibitionism Erotica)
Futa Brides (Futa Honeymoon Surprise 1)(Futa-on-futa, futa-on-female, public fun erotica) (Fuat Honeymoon Surprise)
The Transformation of Eric (The Making of a Sissy Book 1)