The first four books in Karina Halle's Experiment in Terror series are discounted to 0.99. ( Actually, book one is free, but the next 4 books are discounted.)
I loved Evil Genius by Patricia Rice when I read it a couple of years ago, and right now it is discounted to 2.99. Which is a bargain for this novel.
I like Marie Force Gansett Island Series, but I haven't read her Harrington series yet. But it is on my wishlist, and right now Treading Water, book One, is free at Amazon, Smashwords, BN and Kobo.
The Governess Affair by Courtney Milan is also free at the moment. I liked it when I read it last year. ( In fact, I need to get the rest of the series.)
Tarnished Heart by Bec Macallister is free right now. I have heard good things about her, so I'll probably read it soon.