While this is technically not free, costing $1 comes pretty close to it. Book publisher Orbit is running a promotion allowing Kindle owners to download one of their books per month for one dollar.
Almost free eBook for March 2009 is Empress By Karen Miller. It’s a fantasy story of Hekat, who is no more than an unwanted mouth to feed, worth only a few coins from a passing slave trader. But Hekat was not born to be a slave. For her, a different path has been chosen.