There are three books available for free Kindle download from Christian publishers today. They go back to regular prices quickly sometimes, so be sure to check the price at checkout. These are not free for Nook at this time.
Mary's Son: A Tale of Christmas by Darryl Nyznyk (Cross Dove Publishing)
Back on the free list:
Surrender the Wind by Rita Gerlach (Abingdon Press)
Gone to Green by Judy Christie (Abingdon Press)