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.
He's Still In Her Body: a tale of body-swapping (B.H. Wrencher's Bodies)
Sissy Shades of Pink
Cursed With Cock (futanari, dickgirl, public sex and paranormal erotica)
Luna Holdings: A Novel (Paranormal Erotica)
The New Maid (Mistress Beka Sex Stories)
Both Sides, Now An Erotic Transgender Love Story