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.
Femboy's Awakening: An erotic adventure of swords, sorcery, and feminization. (The Femboy Codex Book 1)
Spice up the Night (crossdressing, femdom)
Sweet Release (Bimbo Futanari Transformation Erotica) (Futa on Female Erotica)
Servicing the Debt and other Femdom Stories
Gender Swap Jock (Reluctant Gender Transformation)
Secrets and Guys (Transgender and Genderqueer Erotic Romance Book 0)
The Jennifer Borden trilogy-trilogy: STEAMY She-male Sex & Romance Stories