Barnes & Noble is offering a few free e-books each week. It looks like these will be ‘classics’ such as Call of the Wild, Little Women, etc.–books already in the public domain. These books would be free to owners of B&N’s e-reader–the Nook.
It is my understanding that you can already get these books for free on the Kindle by going to the Gutenberg Project page. I don’t have a Kindle, so I don’t know for certain, but this site seems to suggest that it’s possible.
So to me I see little benefit added to these free books. Granted, if you’re not aware of Project Gutenberg, this may seem like a deal, but I see no reason why this would entice me to buy a Nook over the Kindle.