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.
The Changing Room: A Gender Swap Tale
Crossing (Open Door Love Story Book 1)
fuTA 2: Experimental Threesome (Futa on Female Menage)
Futanari Planet 2: Discovery
Futanari Sorority Adventures: Volume 1-5
Love sex and the whip: Training James, the story of a female led marriage
Hunting Futas: The Holy Futa (Taboo Futanari Erotica)
Swapped And Fertile: Victorian Historical Gender Swap Fertile Erotica
Claiming the Bride: (Cuckolded on His Wedding Day)
Become the Woman of Your Dreams! (Interactive Gender Transformation Feminization Erotica) (Aurora Sparks Interactive Erotica Book 1)
The Metamorphosis of Michael F: A transsexual odyssey of love, revenge and murder