Divorced, Desperate and Dating by Christie Craig (Mystery/Romance) was available from Kindle and elsewhere earlier this month but now it's at kobobooks:
http://www.kobobooks.com/ebook/Divor...2lg/page1.html
It appears several titles from "Love Spell" and "Leisure" are also currently $0. Here are a few picks:
The Cellar by Richard Laymon looks interesting:
Tourists flock to Beast House, but few ever return. Behind the cellar door lurks a creature of pure evil. The author has a half dozen other titles for sale at Kobo.
http://www.kobobooks.com/ebook/The-C...zcg/page1.html
What Burns Within by Sandra Ruttan is a bit "dark":
Child abductions, arson, and rapes. Three series of very different crimes are terrorizing the city. But the evidence suggests that they might all somehow be related. But, again, a couple of other titles are also available.
http://www.kobobooks.com/ebook/What-...0gQ/page1.html
Spying in High Heels by Gemma Halliday sounds more "cozy" mystery:
An L.A. fashionista finds herself in over her head when murder, embezzlement, and a hot detective collide in her life. There are another five titles in the series if you enjoy Halliday's style.
http://www.kobobooks.com/ebook/Spyin...8_w/page1.html
At this link
http://www.kobobooks.com/lists/Free_...iEieHvg-1.html you'll find about 40 titles before hitting PD. Time may be limited!