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.
My Ebony Surprise: Transgender Erotica
She Has a Surprise: Transgender Surprise Erotica Bundle
Masquerade on Poker Night
My Cupid Futa (BBW Futa on Female transgender erotic romance)
Top Secret Swap (Swap Secret Spy Series Book 1)
Hot Cop Gender Swap
Transsexual Love Girl: Transgender | Male Erotica
The Futanari Meets My Girlfriend (What the Futanari Book 2)
Erotic Futagirl Bundle IV