Amazon looks like it is currently marking down 16 books for free. (OK 15 if you don't count the summary of the duct-tape book)
Most (if not all) of these books are the ones that TOR recently gave away for free, so if you missed some, now is the time to get them delivered to your Kindle. I found at least 5 that I had not gotten all ready through the TOR give-away including Old Man's War which I had signed up too late to get.
Just go to Amazon, pull up the list of Kindle books, and sort lowest to highest price. Download away
