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.
Gender Swap Auto Shop(Gender Transformation, Feminization)
Gender Bender Dancers: TG Bundle
Spring Fever (Transgender and Genderqueer Erotic Romance)
Friends of Dorothy (Transgender and Genderqueer Erotic Romance Book 0)
Futanari Demigoddess 8: Siren's Song (Futa on Female Group)
Blackmailing the Boss: A Tale of FinDom, FemDom, Forced Feminization, and so much more
Lisa's Little Whore: A Feminization Rough Sex Bondage Story
Gender Swap Sex Shop (Gender Transformation, Feminization)
Transgender 1: Becoming Becky (Gender Swap Erotica) (The Captive Series Book 34)
House Husband 3: Playing Hostess