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.
Boy Wife 1: Wife For The Night
A Sissy's Delight 1 (Femdom Humiliation Cuckold)
Travails of a Transvestite: How Sean became Sharon, and finally achieved true femininity, after much humiliation and degradation
Milking Macy (Futa on Female Fun)
Transexual Mistress Surprise (Mistress Beka Sex Stories)
Turning The Tables (The Adventures of a Dirty Slut Book 4)
The Gender Bender Mystery Vol. 2 (Gender Transformation Erotica)