http://www.barnesandnoble.com/u/Free...hors/379002210
Seems interesting. Note that it does NOT require a Nook. There's also a piece of downloadable "B&N Reader" software which works on iPhone, Blackberry, PC AND Mac.
The last two probably put you at a disadvantage for getting the "free" books though, since you have to actually SHOW the device to someone in a store to get the voucher.
You can get 1 voucher each week, for five weeks.
The titles in question seem to be major bestsellers, but its five specific ones. You don't really get a choice. The first two are "The No. 1 Ladies Detective Agency" and "Storm Front". So they are old catalog, I guess, but only a few years.