Marta Acosta offers the whole Casa Dracula series for free right now ( ends today), so hurry up and download them. ( I am happy, since this series have been on my wishlist for ages.)
The Accidential Demon Slayer by Angie Fox is also free right now ( I think this is always free, in fact).
Beyond Shame by Kit Rocha is free right now at Smashwords ( with a coupon at Bookbinge). This is one of my favorite erotic romances. But then Kit Rocha is a pseudonym for Moira Rogers.
The Black Swan series by Victoria Danann have gotten a lot of buzz lately, and the first book is free at Smashwords.