Okay, so today, only one book is free, The Sixth Discipline. It's free because of price matching, not because of a Kindle Select promotion, which is why it's free almost everywhere it's for sale.
This latest promotion was only moderately successful. In spite of King of Trees reaching #33 in free Kindle science fiction books, I still gave away only a few hundred copies, over the two days, with almost twice as many on the 28th of February as on March 1st. In addition, the numbers of free downloads for The Sixth Discipline have dropped by a little more than half since March 1.
Interestingly enough, March 1 was when Amazon started a new policy for their affiliates. Amazon affiliates are websites that have a formal arrangement with Amazon; they put links to Amazon products on their pages, and they get paid when people use them. The new policy says that if those websites have too high a percentage of customers clicking free ebook links, they will be penalized finacially. The Digital Reader blog post explains the specifics of it better than I can, but what it means at a very basic level is that links to free Kindle books are now poison for blogs that are Amazon affiliates.
My numbers for the past three days suggest that Amazon's new policy means that it will be much harder for authors to use free promotions successfully. I don't think I'm the only author to notice this, either, because although The Sixth Discipline's numbers have dropped, its ranking is still about the same, which must mean other free Kindle books are suffering the same kind of lack of attention. One of the main benefits of the KDP Select program (which requires that you not sell any ebook versions for that title, except through Kindle) is the ability to do occasional promotions. Since it's now a lot harder to promote those giveaways, what Amazon has given with one hand, they have taken away (at least part of) with the other hand.