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 Aliens (Reluctant Gender Transformation)
Pink Panic (Transgender Guide to the Universe Book 1)
From Bad Boy to Good Girl 1 (Gender Transformation Erotica)
Tricked and Swapped: Becoming a Frat Girl (Gender Transformation, Threesome)
Gender Swap Anthology
Tara My Tranny (Transgender Fiction Book 1)
Three for a New Life
Menage Boxed Set: Threesomes, Mistresses, and a Dominatrix